diff --git a/web/src/App.tsx b/web/src/App.tsx
index d30286c..b6ae377 100644
--- a/web/src/App.tsx
+++ b/web/src/App.tsx
@@ -5,6 +5,9 @@
 
 import { BrowserRouter, Routes, Route, Navigate } from 'react-router-dom';
 import { AdminLayout } from './layouts/AdminLayout';
+import { ProtectedRoute } from './components/auth/ProtectedRoute';
+import { ThemeProvider } from './components/theme';
+import { ToastContainer } from './components/common';
 import {
   FraccionamientosPage,
   FraccionamientoDetailPage,
@@ -18,18 +21,32 @@ import { ConceptosPage, PresupuestosPage, PresupuestoDetailPage, EstimacionesPag
 import { OpportunitiesPage, TendersPage, ProposalsPage, VendorsPage } from './pages/admin/bidding';
 import { IncidentesPage, CapacitacionesPage, InspeccionesPage, InspeccionDetailPage } from './pages/admin/hse';
 import { AvancesObraPage, BitacoraObraPage, ProgramaObraPage, ControlAvancePage } from './pages/admin/obras';
+import {
+  CuentasContablesPage,
+  CuentasPorCobrarPage,
+  CuentasPorPagarPage,
+  PolizasPage,
+  FlujoEfectivoPage,
+  FacturasPage,
+} from './pages/admin/finanzas';
 import { LoginPage } from './pages/auth';
 
 function App() {
   return (
-    <BrowserRouter>
-      <div className="app">
-        <Routes>
+    <ThemeProvider>
+      <BrowserRouter
+        future={{
+          v7_startTransition: true,
+          v7_relativeSplatPath: true,
+        }}
+      >
+        <div className="app min-h-screen bg-background text-foreground transition-colors duration-200">
+          <Routes>
           {/* Ruta principal - redirect to admin dashboard */}
           <Route path="/" element={<Navigate to="/admin/dashboard" replace />} />
 
-          {/* Portal Admin */}
-          <Route path="/admin" element={<AdminLayout />}>
+          {/* Portal Admin - Protected */}
+          <Route path="/admin" element={<ProtectedRoute><AdminLayout /></ProtectedRoute>}>
             <Route index element={<Navigate to="dashboard" replace />} />
 
             {/* Dashboard */}
@@ -81,6 +98,17 @@ function App() {
               <Route path="programa" element={<ProgramaObraPage />} />
               <Route path="bitacora" element={<BitacoraObraPage />} />
             </Route>
+
+            {/* Finanzas */}
+            <Route path="finanzas">
+              <Route index element={<Navigate to="flujo-efectivo" replace />} />
+              <Route path="cuentas" element={<CuentasContablesPage />} />
+              <Route path="polizas" element={<PolizasPage />} />
+              <Route path="cxc" element={<CuentasPorCobrarPage />} />
+              <Route path="cxp" element={<CuentasPorPagarPage />} />
+              <Route path="flujo-efectivo" element={<FlujoEfectivoPage />} />
+              <Route path="facturas" element={<FacturasPage />} />
+            </Route>
           </Route>
 
           {/* Portal Supervisor */}
@@ -95,8 +123,10 @@ function App() {
           {/* 404 */}
           <Route path="*" element={<Navigate to="/" replace />} />
         </Routes>
-      </div>
-    </BrowserRouter>
+        <ToastContainer />
+        </div>
+      </BrowserRouter>
+    </ThemeProvider>
   );
 }
 
diff --git a/web/src/components/common/ActionButtons.tsx b/web/src/components/common/ActionButtons.tsx
index 3d50dde..9cbc86e 100644
--- a/web/src/components/common/ActionButtons.tsx
+++ b/web/src/components/common/ActionButtons.tsx
@@ -15,10 +15,10 @@ interface ActionButtonProps {
 }
 
 const variantClasses = {
-  default: 'text-gray-500 hover:text-blue-600 hover:bg-blue-50',
-  danger: 'text-gray-500 hover:text-red-600 hover:bg-red-50',
-  success: 'text-gray-500 hover:text-green-600 hover:bg-green-50',
-  warning: 'text-gray-500 hover:text-yellow-600 hover:bg-yellow-50',
+  default: 'text-foreground-muted hover:text-primary hover:bg-primary/10 dark:hover:bg-primary/20',
+  danger: 'text-foreground-muted hover:text-red-600 dark:hover:text-red-400 hover:bg-red-50 dark:hover:bg-red-900/20',
+  success: 'text-foreground-muted hover:text-green-600 dark:hover:text-green-400 hover:bg-green-50 dark:hover:bg-green-900/20',
+  warning: 'text-foreground-muted hover:text-yellow-600 dark:hover:text-yellow-400 hover:bg-yellow-50 dark:hover:bg-yellow-900/20',
 };
 
 export function ActionButton({
@@ -127,14 +127,14 @@ export function ActionMenu({ items, className }: ActionMenuProps) {
     <div className={clsx('relative', className)} ref={menuRef}>
       <button
         type="button"
-        className="p-2 text-gray-500 hover:text-gray-700 hover:bg-gray-100 rounded-lg"
+        className="p-2 text-foreground-muted hover:text-foreground hover:bg-background-muted dark:hover:bg-background-emphasis rounded-lg transition-colors"
         onClick={() => setIsOpen(!isOpen)}
       >
         <MoreVertical className="w-4 h-4" />
       </button>
 
       {isOpen && (
-        <div className="absolute right-0 mt-1 w-48 bg-white rounded-lg shadow-lg border py-1 z-10">
+        <div className="absolute right-0 mt-1 w-48 bg-surface-popover dark:bg-surface-popover rounded-lg shadow-lg border border-border dark:border-border py-1 z-dropdown">
           {items.map((item, index) => {
             const Icon = item.icon;
             return (
@@ -142,10 +142,10 @@ export function ActionMenu({ items, className }: ActionMenuProps) {
                 key={index}
                 type="button"
                 className={clsx(
-                  'w-full px-4 py-2 text-left text-sm flex items-center gap-2',
+                  'w-full px-4 py-2 text-left text-sm flex items-center gap-2 transition-colors',
                   item.variant === 'danger'
-                    ? 'text-red-600 hover:bg-red-50'
-                    : 'text-gray-700 hover:bg-gray-50',
+                    ? 'text-red-600 dark:text-red-400 hover:bg-red-50 dark:hover:bg-red-900/20'
+                    : 'text-foreground hover:bg-background-muted dark:hover:bg-background-emphasis',
                   item.disabled && 'opacity-50 cursor-not-allowed'
                 )}
                 onClick={() => {
diff --git a/web/src/components/common/ConfirmDialog.tsx b/web/src/components/common/ConfirmDialog.tsx
index 5a9fed1..b2a9abf 100644
--- a/web/src/components/common/ConfirmDialog.tsx
+++ b/web/src/components/common/ConfirmDialog.tsx
@@ -21,21 +21,21 @@ interface ConfirmDialogProps {
 const variantConfig = {
   danger: {
     icon: AlertTriangle,
-    iconBg: 'bg-red-100',
-    iconColor: 'text-red-600',
-    buttonClass: 'bg-red-600 hover:bg-red-700',
+    iconBg: 'bg-red-100 dark:bg-red-900/30',
+    iconColor: 'text-red-600 dark:text-red-400',
+    buttonClass: 'bg-red-600 hover:bg-red-700 dark:bg-red-700 dark:hover:bg-red-600',
   },
   warning: {
     icon: AlertCircle,
-    iconBg: 'bg-yellow-100',
-    iconColor: 'text-yellow-600',
-    buttonClass: 'bg-yellow-600 hover:bg-yellow-700',
+    iconBg: 'bg-yellow-100 dark:bg-yellow-900/30',
+    iconColor: 'text-yellow-600 dark:text-yellow-400',
+    buttonClass: 'bg-yellow-600 hover:bg-yellow-700 dark:bg-yellow-700 dark:hover:bg-yellow-600',
   },
   info: {
     icon: Info,
-    iconBg: 'bg-blue-100',
-    iconColor: 'text-blue-600',
-    buttonClass: 'bg-blue-600 hover:bg-blue-700',
+    iconBg: 'bg-blue-100 dark:bg-blue-900/30',
+    iconColor: 'text-blue-600 dark:text-blue-400',
+    buttonClass: 'bg-primary hover:bg-primary-hover',
   },
 };
 
@@ -75,12 +75,12 @@ export function ConfirmDialog({
         >
           <Icon className={clsx('w-6 h-6', config.iconColor)} />
         </div>
-        <h3 className="text-lg font-semibold text-gray-900 mb-2">{title}</h3>
-        <p className="text-gray-600 mb-6">{message}</p>
+        <h3 className="text-lg font-semibold text-foreground mb-2">{title}</h3>
+        <p className="text-foreground-muted mb-6">{message}</p>
         <ModalFooter className="w-full">
           <button
             type="button"
-            className="flex-1 px-4 py-2 text-gray-700 border rounded-lg hover:bg-gray-50 disabled:opacity-50"
+            className="flex-1 px-4 py-2 text-foreground border border-border dark:border-border rounded-lg hover:bg-background-muted dark:hover:bg-background-emphasis disabled:opacity-50 transition-colors"
             onClick={onClose}
             disabled={isLoading}
           >
diff --git a/web/src/components/common/DataTable.tsx b/web/src/components/common/DataTable.tsx
index 51caca1..0a22fbd 100644
--- a/web/src/components/common/DataTable.tsx
+++ b/web/src/components/common/DataTable.tsx
@@ -91,13 +91,13 @@ export function DataTable<T>({
     : 0;
 
   return (
-    <div className={clsx('bg-white rounded-lg shadow-sm overflow-hidden', className)}>
+    <div className={clsx('bg-surface-card dark:bg-surface-card rounded-lg shadow-sm overflow-hidden', className)}>
       {/* Loading State */}
       {isLoading && <LoadingOverlay />}
 
       {/* Error State */}
       {!isLoading && error && (
-        <div className="p-8 text-center text-red-500">{error}</div>
+        <div className="p-8 text-center text-red-500 dark:text-red-400">{error}</div>
       )}
 
       {/* Empty State */}
@@ -114,14 +114,14 @@ export function DataTable<T>({
       {!isLoading && !error && data.length > 0 && (
         <>
           <div className="overflow-x-auto">
-            <table className="min-w-full divide-y divide-gray-200">
-              <thead className="bg-gray-50">
+            <table className="min-w-full divide-y divide-border dark:divide-border">
+              <thead className="bg-background-subtle dark:bg-background-emphasis">
                 <tr>
                   {columns.map((column) => (
                     <th
                       key={column.key}
                       className={clsx(
-                        'px-6 py-3 text-xs font-medium text-gray-500 uppercase tracking-wider',
+                        'px-6 py-3 text-xs font-medium text-foreground-muted uppercase tracking-wider',
                         alignClasses[column.align || 'left'],
                         column.className
                       )}
@@ -132,12 +132,12 @@ export function DataTable<T>({
                   ))}
                 </tr>
               </thead>
-              <tbody className="bg-white divide-y divide-gray-200">
+              <tbody className="bg-surface-card dark:bg-surface-card divide-y divide-border dark:divide-border">
                 {data.map((item, index) => (
                   <tr
                     key={getRowKey(item, index)}
                     className={clsx(
-                      'hover:bg-gray-50 transition-colors',
+                      'hover:bg-background-muted dark:hover:bg-background-emphasis transition-colors',
                       onRowClick && 'cursor-pointer',
                       getRowClassName(item, index)
                     )}
@@ -147,7 +147,7 @@ export function DataTable<T>({
                       <td
                         key={column.key}
                         className={clsx(
-                          'px-6 py-4 whitespace-nowrap text-sm',
+                          'px-6 py-4 whitespace-nowrap text-sm text-foreground',
                           alignClasses[column.align || 'left'],
                           column.className
                         )}
@@ -165,34 +165,34 @@ export function DataTable<T>({
 
           {/* Pagination */}
           {pagination && totalPages > 1 && (
-            <div className="px-6 py-3 border-t bg-gray-50 flex items-center justify-between">
-              <div className="text-sm text-gray-500">
+            <div className="px-6 py-3 border-t border-border dark:border-border bg-background-subtle dark:bg-background-emphasis flex items-center justify-between">
+              <div className="text-sm text-foreground-muted">
                 Mostrando {startItem} a {endItem} de {pagination.total} resultados
               </div>
               <div className="flex items-center gap-2">
                 <button
                   type="button"
                   className={clsx(
-                    'p-2 rounded-lg border',
+                    'p-2 rounded-lg border border-border dark:border-border transition-colors',
                     pagination.page === 1
-                      ? 'text-gray-300 cursor-not-allowed'
-                      : 'text-gray-600 hover:bg-gray-100'
+                      ? 'text-foreground-disabled cursor-not-allowed'
+                      : 'text-foreground hover:bg-background-muted dark:hover:bg-background-emphasis'
                   )}
                   onClick={() => onPageChange?.(pagination.page - 1)}
                   disabled={pagination.page === 1}
                 >
                   <ChevronLeft className="w-5 h-5" />
                 </button>
-                <span className="text-sm text-gray-600">
+                <span className="text-sm text-foreground">
                   Página {pagination.page} de {totalPages}
                 </span>
                 <button
                   type="button"
                   className={clsx(
-                    'p-2 rounded-lg border',
+                    'p-2 rounded-lg border border-border dark:border-border transition-colors',
                     pagination.page === totalPages
-                      ? 'text-gray-300 cursor-not-allowed'
-                      : 'text-gray-600 hover:bg-gray-100'
+                      ? 'text-foreground-disabled cursor-not-allowed'
+                      : 'text-foreground hover:bg-background-muted dark:hover:bg-background-emphasis'
                   )}
                   onClick={() => onPageChange?.(pagination.page + 1)}
                   disabled={pagination.page === totalPages}
diff --git a/web/src/components/common/EmptyState.tsx b/web/src/components/common/EmptyState.tsx
index 5cd2fe3..3a14cb2 100644
--- a/web/src/components/common/EmptyState.tsx
+++ b/web/src/components/common/EmptyState.tsx
@@ -20,11 +20,11 @@ export function EmptyState({
 }: EmptyStateProps) {
   return (
     <div className="flex flex-col items-center justify-center p-8 text-center">
-      <div className="w-16 h-16 flex items-center justify-center rounded-full bg-gray-100 mb-4">
-        {icon ?? <FileX className="w-8 h-8 text-gray-400" />}
+      <div className="w-16 h-16 flex items-center justify-center rounded-full bg-background-muted dark:bg-background-emphasis mb-4">
+        {icon ?? <FileX className="w-8 h-8 text-foreground-muted" />}
       </div>
-      <h3 className="text-lg font-medium text-gray-900 mb-1">{title}</h3>
-      <p className="text-gray-500 mb-4 max-w-sm">{description}</p>
+      <h3 className="text-lg font-medium text-foreground mb-1">{title}</h3>
+      <p className="text-foreground-muted mb-4 max-w-sm">{description}</p>
       {action}
     </div>
   );
diff --git a/web/src/components/common/FormField.tsx b/web/src/components/common/FormField.tsx
index a619e06..4c92ae5 100644
--- a/web/src/components/common/FormField.tsx
+++ b/web/src/components/common/FormField.tsx
@@ -25,27 +25,27 @@ export const TextInput = forwardRef<HTMLInputElement, TextInputProps>(
         {label && (
           <label
             htmlFor={inputId}
-            className="block text-sm font-medium text-gray-700 mb-1"
+            className="block text-sm font-medium text-foreground mb-1"
           >
             {label}
-            {required && <span className="text-red-500 ml-1">*</span>}
+            {required && <span className="text-red-500 dark:text-red-400 ml-1">*</span>}
           </label>
         )}
         <input
           ref={ref}
           id={inputId}
           className={clsx(
-            'w-full px-3 py-2 border rounded-lg transition-colors',
-            'focus:ring-2 focus:ring-blue-500 focus:border-blue-500',
-            error ? 'border-red-500' : 'border-gray-300',
+            'w-full px-3 py-2 border rounded-lg transition-colors bg-surface-card dark:bg-surface-card text-foreground placeholder:text-foreground-muted',
+            'focus:ring-2 focus:ring-primary focus:border-primary',
+            error ? 'border-red-500 dark:border-red-400' : 'border-border dark:border-border',
             className
           )}
           {...props}
         />
         {hint && !error && (
-          <p className="mt-1 text-sm text-gray-500">{hint}</p>
+          <p className="mt-1 text-sm text-foreground-muted">{hint}</p>
         )}
-        {error && <p className="mt-1 text-sm text-red-600">{error}</p>}
+        {error && <p className="mt-1 text-sm text-red-600 dark:text-red-400">{error}</p>}
       </div>
     );
   }
@@ -68,19 +68,19 @@ export const SelectField = forwardRef<HTMLSelectElement, SelectFieldProps>(
         {label && (
           <label
             htmlFor={selectId}
-            className="block text-sm font-medium text-gray-700 mb-1"
+            className="block text-sm font-medium text-foreground mb-1"
           >
             {label}
-            {required && <span className="text-red-500 ml-1">*</span>}
+            {required && <span className="text-red-500 dark:text-red-400 ml-1">*</span>}
           </label>
         )}
         <select
           ref={ref}
           id={selectId}
           className={clsx(
-            'w-full px-3 py-2 border rounded-lg transition-colors',
-            'focus:ring-2 focus:ring-blue-500 focus:border-blue-500',
-            error ? 'border-red-500' : 'border-gray-300',
+            'w-full px-3 py-2 border rounded-lg transition-colors bg-surface-card dark:bg-surface-card text-foreground',
+            'focus:ring-2 focus:ring-primary focus:border-primary',
+            error ? 'border-red-500 dark:border-red-400' : 'border-border dark:border-border',
             className
           )}
           {...props}
@@ -101,9 +101,9 @@ export const SelectField = forwardRef<HTMLSelectElement, SelectFieldProps>(
           ))}
         </select>
         {hint && !error && (
-          <p className="mt-1 text-sm text-gray-500">{hint}</p>
+          <p className="mt-1 text-sm text-foreground-muted">{hint}</p>
         )}
-        {error && <p className="mt-1 text-sm text-red-600">{error}</p>}
+        {error && <p className="mt-1 text-sm text-red-600 dark:text-red-400">{error}</p>}
       </div>
     );
   }
@@ -123,10 +123,10 @@ export const TextareaField = forwardRef<HTMLTextAreaElement, TextareaFieldProps>
         {label && (
           <label
             htmlFor={textareaId}
-            className="block text-sm font-medium text-gray-700 mb-1"
+            className="block text-sm font-medium text-foreground mb-1"
           >
             {label}
-            {required && <span className="text-red-500 ml-1">*</span>}
+            {required && <span className="text-red-500 dark:text-red-400 ml-1">*</span>}
           </label>
         )}
         <textarea
@@ -134,17 +134,17 @@ export const TextareaField = forwardRef<HTMLTextAreaElement, TextareaFieldProps>
           id={textareaId}
           rows={rows}
           className={clsx(
-            'w-full px-3 py-2 border rounded-lg transition-colors',
-            'focus:ring-2 focus:ring-blue-500 focus:border-blue-500',
-            error ? 'border-red-500' : 'border-gray-300',
+            'w-full px-3 py-2 border rounded-lg transition-colors bg-surface-card dark:bg-surface-card text-foreground placeholder:text-foreground-muted',
+            'focus:ring-2 focus:ring-primary focus:border-primary',
+            error ? 'border-red-500 dark:border-red-400' : 'border-border dark:border-border',
             className
           )}
           {...props}
         />
         {hint && !error && (
-          <p className="mt-1 text-sm text-gray-500">{hint}</p>
+          <p className="mt-1 text-sm text-foreground-muted">{hint}</p>
         )}
-        {error && <p className="mt-1 text-sm text-red-600">{error}</p>}
+        {error && <p className="mt-1 text-sm text-red-600 dark:text-red-400">{error}</p>}
       </div>
     );
   }
@@ -169,8 +169,8 @@ export const CheckboxField = forwardRef<HTMLInputElement, CheckboxFieldProps>(
             id={checkboxId}
             type="checkbox"
             className={clsx(
-              'h-4 w-4 rounded border-gray-300 text-blue-600',
-              'focus:ring-2 focus:ring-blue-500',
+              'h-4 w-4 rounded border-border dark:border-border text-primary',
+              'focus:ring-2 focus:ring-primary',
               className
             )}
             {...props}
@@ -181,17 +181,17 @@ export const CheckboxField = forwardRef<HTMLInputElement, CheckboxFieldProps>(
             {label && (
               <label
                 htmlFor={checkboxId}
-                className="text-sm font-medium text-gray-700"
+                className="text-sm font-medium text-foreground"
               >
                 {label}
               </label>
             )}
             {description && (
-              <p className="text-sm text-gray-500">{description}</p>
+              <p className="text-sm text-foreground-muted">{description}</p>
             )}
           </div>
         )}
-        {error && <p className="mt-1 text-sm text-red-600">{error}</p>}
+        {error && <p className="mt-1 text-sm text-red-600 dark:text-red-400">{error}</p>}
       </div>
     );
   }
diff --git a/web/src/components/common/LoadingSpinner.tsx b/web/src/components/common/LoadingSpinner.tsx
index a485b4e..8d67a22 100644
--- a/web/src/components/common/LoadingSpinner.tsx
+++ b/web/src/components/common/LoadingSpinner.tsx
@@ -19,7 +19,7 @@ export function LoadingSpinner({ size = 'md', className }: LoadingSpinnerProps)
   return (
     <div
       className={clsx(
-        'animate-spin rounded-full border-2 border-gray-300 border-t-blue-600',
+        'animate-spin rounded-full border-2 border-border dark:border-border-emphasis border-t-primary',
         sizeClasses[size],
         className
       )}
@@ -39,7 +39,7 @@ export function LoadingOverlay({ message = 'Cargando...' }: LoadingOverlayProps)
   return (
     <div className="flex flex-col items-center justify-center p-8">
       <LoadingSpinner size="lg" />
-      <p className="mt-4 text-gray-500">{message}</p>
+      <p className="mt-4 text-foreground-muted">{message}</p>
     </div>
   );
 }
diff --git a/web/src/components/common/Modal.tsx b/web/src/components/common/Modal.tsx
index 16f9295..b9613cf 100644
--- a/web/src/components/common/Modal.tsx
+++ b/web/src/components/common/Modal.tsx
@@ -64,7 +64,7 @@ export function Modal({
     <div className="fixed inset-0 z-50 overflow-y-auto">
       {/* Overlay */}
       <div
-        className="fixed inset-0 bg-black bg-opacity-50 transition-opacity"
+        className="fixed inset-0 bg-foreground/50 dark:bg-black/70 transition-opacity"
         onClick={closeOnOverlayClick ? onClose : undefined}
         aria-hidden="true"
       />
@@ -73,21 +73,21 @@ export function Modal({
       <div className="flex min-h-full items-center justify-center p-4">
         <div
           className={clsx(
-            'relative w-full bg-white rounded-lg shadow-xl',
+            'relative w-full bg-surface-card dark:bg-surface-card rounded-lg shadow-xl',
             sizeClasses[size]
           )}
           onClick={(e) => e.stopPropagation()}
         >
           {/* Header */}
           {(title || showCloseButton) && (
-            <div className="flex items-center justify-between px-6 py-4 border-b">
+            <div className="flex items-center justify-between px-6 py-4 border-b border-border dark:border-border">
               {title && (
-                <h3 className="text-lg font-semibold text-gray-900">{title}</h3>
+                <h3 className="text-lg font-semibold text-foreground">{title}</h3>
               )}
               {showCloseButton && (
                 <button
                   type="button"
-                  className="p-2 -mr-2 text-gray-400 hover:text-gray-500 hover:bg-gray-100 rounded-lg"
+                  className="p-2 -mr-2 text-foreground-muted hover:text-foreground hover:bg-background-muted dark:hover:bg-background-emphasis rounded-lg transition-colors"
                   onClick={onClose}
                 >
                   <X className="w-5 h-5" />
@@ -97,11 +97,11 @@ export function Modal({
           )}
 
           {/* Body */}
-          <div className="px-6 py-4 max-h-[70vh] overflow-y-auto">{children}</div>
+          <div className="px-6 py-4 max-h-[70vh] overflow-y-auto text-foreground">{children}</div>
 
           {/* Footer */}
           {footer && (
-            <div className="px-6 py-4 border-t bg-gray-50 rounded-b-lg">
+            <div className="px-6 py-4 border-t border-border dark:border-border bg-background-subtle dark:bg-background-emphasis rounded-b-lg">
               {footer}
             </div>
           )}
diff --git a/web/src/components/common/PageHeader.tsx b/web/src/components/common/PageHeader.tsx
index 2656983..7574a7b 100644
--- a/web/src/components/common/PageHeader.tsx
+++ b/web/src/components/common/PageHeader.tsx
@@ -25,8 +25,8 @@ export function PageHeader({
       {breadcrumbs && <div className="mb-2">{breadcrumbs}</div>}
       <div className="flex items-center justify-between">
         <div>
-          <h1 className="text-2xl font-bold text-gray-900">{title}</h1>
-          {description && <p className="text-gray-600 mt-1">{description}</p>}
+          <h1 className="text-2xl font-bold text-foreground">{title}</h1>
+          {description && <p className="text-foreground-muted mt-1">{description}</p>}
         </div>
         {actions && <div className="flex items-center gap-3">{actions}</div>}
       </div>
@@ -52,8 +52,8 @@ export function PageHeaderAction({
   type = 'button',
 }: PageHeaderActionProps) {
   const variantClasses = {
-    primary: 'bg-blue-600 text-white hover:bg-blue-700',
-    secondary: 'bg-white text-gray-700 border hover:bg-gray-50',
+    primary: 'bg-primary text-white hover:bg-primary-hover',
+    secondary: 'bg-surface-card dark:bg-surface-card text-foreground border border-border dark:border-border hover:bg-background-muted dark:hover:bg-background-emphasis',
   };
 
   return (
diff --git a/web/src/components/common/SearchInput.tsx b/web/src/components/common/SearchInput.tsx
index 96e92a2..bd7a46a 100644
--- a/web/src/components/common/SearchInput.tsx
+++ b/web/src/components/common/SearchInput.tsx
@@ -47,11 +47,11 @@ export function SearchInput({
 
   return (
     <div className={clsx('relative', className)}>
-      <Search className="absolute left-3 top-1/2 -translate-y-1/2 w-5 h-5 text-gray-400" />
+      <Search className="absolute left-3 top-1/2 -translate-y-1/2 w-5 h-5 text-foreground-muted" />
       <input
         type="text"
         placeholder={placeholder}
-        className="w-full pl-10 pr-10 py-2 border rounded-lg focus:ring-2 focus:ring-blue-500 focus:border-blue-500"
+        className="w-full pl-10 pr-10 py-2 border border-border dark:border-border rounded-lg bg-surface-card dark:bg-surface-card text-foreground placeholder:text-foreground-muted focus:ring-2 focus:ring-primary focus:border-primary transition-colors"
         value={localValue}
         onChange={(e) => setLocalValue(e.target.value)}
         autoFocus={autoFocus}
@@ -60,7 +60,7 @@ export function SearchInput({
         <button
           type="button"
           onClick={handleClear}
-          className="absolute right-3 top-1/2 -translate-y-1/2 p-1 text-gray-400 hover:text-gray-600"
+          className="absolute right-3 top-1/2 -translate-y-1/2 p-1 text-foreground-muted hover:text-foreground transition-colors"
         >
           <X className="w-4 h-4" />
         </button>
diff --git a/web/src/components/common/StatusBadge.tsx b/web/src/components/common/StatusBadge.tsx
index 55c7f63..c47d778 100644
--- a/web/src/components/common/StatusBadge.tsx
+++ b/web/src/components/common/StatusBadge.tsx
@@ -14,15 +14,15 @@ interface StatusBadgeProps {
 }
 
 const colorClasses: Record<StatusColor, { bg: string; text: string; dot: string }> = {
-  gray: { bg: 'bg-gray-100', text: 'text-gray-800', dot: 'bg-gray-500' },
-  green: { bg: 'bg-green-100', text: 'text-green-800', dot: 'bg-green-500' },
-  yellow: { bg: 'bg-yellow-100', text: 'text-yellow-800', dot: 'bg-yellow-500' },
-  red: { bg: 'bg-red-100', text: 'text-red-800', dot: 'bg-red-500' },
-  blue: { bg: 'bg-blue-100', text: 'text-blue-800', dot: 'bg-blue-500' },
-  purple: { bg: 'bg-purple-100', text: 'text-purple-800', dot: 'bg-purple-500' },
-  orange: { bg: 'bg-orange-100', text: 'text-orange-800', dot: 'bg-orange-500' },
-  pink: { bg: 'bg-pink-100', text: 'text-pink-800', dot: 'bg-pink-500' },
-  indigo: { bg: 'bg-indigo-100', text: 'text-indigo-800', dot: 'bg-indigo-500' },
+  gray: { bg: 'bg-gray-100 dark:bg-gray-800', text: 'text-gray-800 dark:text-gray-200', dot: 'bg-gray-500' },
+  green: { bg: 'bg-green-100 dark:bg-green-900/30', text: 'text-green-800 dark:text-green-300', dot: 'bg-green-500' },
+  yellow: { bg: 'bg-yellow-100 dark:bg-yellow-900/30', text: 'text-yellow-800 dark:text-yellow-300', dot: 'bg-yellow-500' },
+  red: { bg: 'bg-red-100 dark:bg-red-900/30', text: 'text-red-800 dark:text-red-300', dot: 'bg-red-500' },
+  blue: { bg: 'bg-blue-100 dark:bg-blue-900/30', text: 'text-blue-800 dark:text-blue-300', dot: 'bg-blue-500' },
+  purple: { bg: 'bg-purple-100 dark:bg-purple-900/30', text: 'text-purple-800 dark:text-purple-300', dot: 'bg-purple-500' },
+  orange: { bg: 'bg-orange-100 dark:bg-orange-900/30', text: 'text-orange-800 dark:text-orange-300', dot: 'bg-orange-500' },
+  pink: { bg: 'bg-pink-100 dark:bg-pink-900/30', text: 'text-pink-800 dark:text-pink-300', dot: 'bg-pink-500' },
+  indigo: { bg: 'bg-indigo-100 dark:bg-indigo-900/30', text: 'text-indigo-800 dark:text-indigo-300', dot: 'bg-indigo-500' },
 };
 
 const sizeClasses = {
diff --git a/web/src/components/common/Toast.tsx b/web/src/components/common/Toast.tsx
new file mode 100644
index 0000000..58c4268
--- /dev/null
+++ b/web/src/components/common/Toast.tsx
@@ -0,0 +1,116 @@
+/**
+ * Toast - Global notification component
+ */
+
+import { useEffect, useCallback } from 'react';
+import { X, CheckCircle, AlertTriangle, AlertCircle, Info } from 'lucide-react';
+import clsx from 'clsx';
+import { useToastStore, type ToastType, type Toast as ToastItem } from '../../stores/toastStore';
+
+const toastConfig: Record<ToastType, {
+  icon: typeof CheckCircle;
+  bgClass: string;
+  iconClass: string;
+  borderClass: string;
+}> = {
+  success: {
+    icon: CheckCircle,
+    bgClass: 'bg-green-50 dark:bg-green-900/20',
+    iconClass: 'text-green-500 dark:text-green-400',
+    borderClass: 'border-green-200 dark:border-green-800',
+  },
+  error: {
+    icon: AlertCircle,
+    bgClass: 'bg-red-50 dark:bg-red-900/20',
+    iconClass: 'text-red-500 dark:text-red-400',
+    borderClass: 'border-red-200 dark:border-red-800',
+  },
+  warning: {
+    icon: AlertTriangle,
+    bgClass: 'bg-yellow-50 dark:bg-yellow-900/20',
+    iconClass: 'text-yellow-500 dark:text-yellow-400',
+    borderClass: 'border-yellow-200 dark:border-yellow-800',
+  },
+  info: {
+    icon: Info,
+    bgClass: 'bg-blue-50 dark:bg-blue-900/20',
+    iconClass: 'text-blue-500 dark:text-blue-400',
+    borderClass: 'border-blue-200 dark:border-blue-800',
+  },
+};
+
+interface ToastItemProps {
+  toast: ToastItem;
+  onDismiss: (id: string) => void;
+}
+
+function ToastItemComponent({ toast, onDismiss }: ToastItemProps) {
+  const config = toastConfig[toast.type];
+  const Icon = config.icon;
+
+  useEffect(() => {
+    if (toast.duration && toast.duration > 0) {
+      const timer = setTimeout(() => {
+        onDismiss(toast.id);
+      }, toast.duration);
+      return () => clearTimeout(timer);
+    }
+  }, [toast.id, toast.duration, onDismiss]);
+
+  return (
+    <div
+      className={clsx(
+        'flex items-start gap-3 p-4 rounded-lg border shadow-lg max-w-sm w-full',
+        'transform transition-all duration-300 ease-out',
+        config.bgClass,
+        config.borderClass
+      )}
+      role="alert"
+    >
+      <Icon className={clsx('w-5 h-5 flex-shrink-0 mt-0.5', config.iconClass)} />
+      <div className="flex-1 min-w-0">
+        {toast.title && (
+          <p className="text-sm font-semibold text-foreground">{toast.title}</p>
+        )}
+        <p className="text-sm text-foreground-muted">{toast.message}</p>
+      </div>
+      <button
+        type="button"
+        onClick={() => onDismiss(toast.id)}
+        className="flex-shrink-0 p-1 text-foreground-muted hover:text-foreground rounded transition-colors"
+        aria-label="Cerrar notificación"
+      >
+        <X className="w-4 h-4" />
+      </button>
+    </div>
+  );
+}
+
+export function ToastContainer() {
+  const { toasts, removeToast } = useToastStore();
+
+  const handleDismiss = useCallback(
+    (id: string) => removeToast(id),
+    [removeToast]
+  );
+
+  if (toasts.length === 0) return null;
+
+  return (
+    <div
+      className="fixed bottom-4 right-4 z-toast flex flex-col gap-2"
+      aria-live="polite"
+      aria-label="Notificaciones"
+    >
+      {toasts.map((toast) => (
+        <ToastItemComponent
+          key={toast.id}
+          toast={toast}
+          onDismiss={handleDismiss}
+        />
+      ))}
+    </div>
+  );
+}
+
+export { ToastItemComponent as ToastItem };
diff --git a/web/src/components/common/index.ts b/web/src/components/common/index.ts
index 606e4c0..71076f0 100644
--- a/web/src/components/common/index.ts
+++ b/web/src/components/common/index.ts
@@ -34,3 +34,6 @@ export { ActionButton, ActionButtons, ActionMenu } from './ActionButtons';
 // Data Display
 export { DataTable } from './DataTable';
 export type { DataTableColumn, DataTablePagination } from './DataTable';
+
+// Toast Notifications
+export { ToastContainer, ToastItem } from './Toast';
diff --git a/web/src/components/theme/ThemeProvider.tsx b/web/src/components/theme/ThemeProvider.tsx
new file mode 100644
index 0000000..59ba647
--- /dev/null
+++ b/web/src/components/theme/ThemeProvider.tsx
@@ -0,0 +1,69 @@
+/**
+ * ThemeProvider Component
+ * Inicializa el tema y proporciona el contexto
+ */
+
+import { useEffect, type ReactNode } from 'react';
+import { useThemeStore, type Theme } from '../../stores/themeStore';
+
+interface ThemeProviderProps {
+  children: ReactNode;
+  defaultTheme?: Theme;
+}
+
+/**
+ * Hook para acceder al tema actual y funciones de cambio
+ */
+export function useTheme() {
+  const theme = useThemeStore((state) => state.theme);
+  const resolvedTheme = useThemeStore((state) => state.resolvedTheme);
+  const setTheme = useThemeStore((state) => state.setTheme);
+  const toggleTheme = useThemeStore((state) => state.toggleTheme);
+
+  return {
+    theme,
+    resolvedTheme,
+    setTheme,
+    toggleTheme,
+    isDark: resolvedTheme === 'dark',
+    isLight: resolvedTheme === 'light',
+    isSystem: theme === 'system',
+  };
+}
+
+/**
+ * ThemeProvider - Envuelve la aplicación para gestionar el tema
+ */
+export function ThemeProvider({ children, defaultTheme = 'system' }: ThemeProviderProps) {
+  const { theme, setTheme } = useTheme();
+
+  // Inicializar tema por defecto si no hay uno guardado
+  useEffect(() => {
+    // Solo establecer el tema por defecto en la primera carga
+    // si no hay tema guardado en localStorage
+    const stored = localStorage.getItem('erp-construccion-theme');
+    if (!stored && theme === 'system') {
+      setTheme(defaultTheme);
+    }
+  }, []);
+
+  // Aplicar tema inicial
+  useEffect(() => {
+    const resolvedTheme = theme === 'system'
+      ? (window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light')
+      : theme;
+
+    const root = document.documentElement;
+    if (resolvedTheme === 'dark') {
+      root.classList.add('dark');
+      root.setAttribute('data-theme', 'dark');
+    } else {
+      root.classList.remove('dark');
+      root.setAttribute('data-theme', 'light');
+    }
+  }, [theme]);
+
+  return <>{children}</>;
+}
+
+export default ThemeProvider;
diff --git a/web/src/components/theme/ThemeToggle.tsx b/web/src/components/theme/ThemeToggle.tsx
new file mode 100644
index 0000000..dbad43a
--- /dev/null
+++ b/web/src/components/theme/ThemeToggle.tsx
@@ -0,0 +1,170 @@
+/**
+ * ThemeToggle Component
+ * Botón para cambiar entre temas light/dark/system
+ */
+
+import { Sun, Moon, Monitor } from 'lucide-react';
+import { useTheme } from './ThemeProvider';
+import type { Theme } from '../../stores/themeStore';
+
+interface ThemeToggleProps {
+  /** Mostrar solo toggle light/dark (sin opción system) */
+  simple?: boolean;
+  /** Tamaño del icono */
+  size?: 'sm' | 'md' | 'lg';
+  /** Clase adicional */
+  className?: string;
+}
+
+const iconSizes = {
+  sm: 16,
+  md: 20,
+  lg: 24,
+};
+
+/**
+ * ThemeToggle simple (solo light/dark)
+ */
+export function ThemeToggle({ simple = false, size = 'md', className = '' }: ThemeToggleProps) {
+  const { theme, resolvedTheme, setTheme, toggleTheme } = useTheme();
+  const iconSize = iconSizes[size];
+
+  if (simple) {
+    return (
+      <button
+        type="button"
+        onClick={toggleTheme}
+        className={`
+          inline-flex items-center justify-center
+          p-2 rounded-md
+          text-foreground-muted hover:text-foreground
+          hover:bg-background-muted
+          focus:outline-none focus:ring-2 focus:ring-primary focus:ring-offset-2
+          transition-colors duration-150
+          ${className}
+        `}
+        aria-label={resolvedTheme === 'dark' ? 'Cambiar a tema claro' : 'Cambiar a tema oscuro'}
+      >
+        {resolvedTheme === 'dark' ? (
+          <Sun size={iconSize} aria-hidden="true" />
+        ) : (
+          <Moon size={iconSize} aria-hidden="true" />
+        )}
+      </button>
+    );
+  }
+
+  const options: { value: Theme; label: string; icon: typeof Sun }[] = [
+    { value: 'light', label: 'Claro', icon: Sun },
+    { value: 'dark', label: 'Oscuro', icon: Moon },
+    { value: 'system', label: 'Sistema', icon: Monitor },
+  ];
+
+  return (
+    <div className={`inline-flex rounded-md shadow-sm ${className}`} role="group">
+      {options.map(({ value, label, icon: Icon }) => (
+        <button
+          key={value}
+          type="button"
+          onClick={() => setTheme(value)}
+          className={`
+            inline-flex items-center justify-center gap-1.5
+            px-3 py-2
+            text-sm font-medium
+            border
+            first:rounded-l-md last:rounded-r-md
+            focus:outline-none focus:ring-2 focus:ring-primary focus:ring-offset-2
+            transition-colors duration-150
+            ${
+              theme === value
+                ? 'bg-primary text-white border-primary'
+                : 'bg-surface-card text-foreground border-border hover:bg-background-muted'
+            }
+          `}
+          aria-pressed={theme === value}
+          aria-label={`Tema ${label}`}
+        >
+          <Icon size={16} aria-hidden="true" />
+          <span className="hidden sm:inline">{label}</span>
+        </button>
+      ))}
+    </div>
+  );
+}
+
+/**
+ * ThemeDropdown - Menú desplegable para seleccionar tema
+ */
+export function ThemeDropdown({ size = 'md', className = '' }: Omit<ThemeToggleProps, 'simple'>) {
+  const { theme, resolvedTheme, setTheme } = useTheme();
+  const iconSize = iconSizes[size];
+
+  const CurrentIcon = resolvedTheme === 'dark' ? Moon : Sun;
+
+  return (
+    <div className={`relative inline-block ${className}`}>
+      <button
+        type="button"
+        className={`
+          inline-flex items-center justify-center
+          p-2 rounded-md
+          text-foreground-muted hover:text-foreground
+          hover:bg-background-muted
+          focus:outline-none focus:ring-2 focus:ring-primary focus:ring-offset-2
+          transition-colors duration-150
+          peer
+        `}
+        aria-label="Seleccionar tema"
+        aria-haspopup="true"
+      >
+        <CurrentIcon size={iconSize} aria-hidden="true" />
+      </button>
+
+      {/* Dropdown menu (visible on hover/focus) */}
+      <div
+        className={`
+          absolute right-0 top-full mt-1
+          w-36 py-1
+          bg-surface-popover border border-border rounded-md shadow-lg
+          opacity-0 invisible
+          peer-hover:opacity-100 peer-hover:visible
+          peer-focus:opacity-100 peer-focus:visible
+          hover:opacity-100 hover:visible
+          transition-all duration-150
+          z-dropdown
+        `}
+        role="menu"
+      >
+        {[
+          { value: 'light' as Theme, label: 'Claro', icon: Sun },
+          { value: 'dark' as Theme, label: 'Oscuro', icon: Moon },
+          { value: 'system' as Theme, label: 'Sistema', icon: Monitor },
+        ].map(({ value, label, icon: Icon }) => (
+          <button
+            key={value}
+            type="button"
+            onClick={() => setTheme(value)}
+            className={`
+              w-full flex items-center gap-2 px-3 py-2 text-sm
+              ${
+                theme === value
+                  ? 'bg-primary/10 text-primary'
+                  : 'text-foreground hover:bg-background-muted'
+              }
+              transition-colors duration-150
+            `}
+            role="menuitem"
+          >
+            <Icon size={16} aria-hidden="true" />
+            {label}
+            {theme === value && (
+              <span className="ml-auto text-primary">✓</span>
+            )}
+          </button>
+        ))}
+      </div>
+    </div>
+  );
+}
+
+export default ThemeToggle;
diff --git a/web/src/components/theme/index.ts b/web/src/components/theme/index.ts
new file mode 100644
index 0000000..5a11f81
--- /dev/null
+++ b/web/src/components/theme/index.ts
@@ -0,0 +1,8 @@
+/**
+ * Theme Components
+ * Exportaciones para gestión de tema
+ */
+
+export { ThemeProvider, useTheme } from './ThemeProvider';
+export { ThemeToggle, ThemeDropdown } from './ThemeToggle';
+export type { Theme } from '../../stores/themeStore';
diff --git a/web/src/hooks/index.ts b/web/src/hooks/index.ts
index e2bf92e..4d38b05 100644
--- a/web/src/hooks/index.ts
+++ b/web/src/hooks/index.ts
@@ -5,3 +5,5 @@ export * from './useReports';
 export * from './useBidding';
 export * from './useHSE';
 export * from './useProgress';
+export * from './useFinance';
+export * from './useToast';
diff --git a/web/src/hooks/useToast.ts b/web/src/hooks/useToast.ts
new file mode 100644
index 0000000..523ccf2
--- /dev/null
+++ b/web/src/hooks/useToast.ts
@@ -0,0 +1,68 @@
+/**
+ * useToast Hook - Simplified interface for toast notifications
+ */
+
+import { useCallback } from 'react';
+import { useToastStore, type ToastType } from '../stores/toastStore';
+
+const DEFAULT_DURATION = 5000;
+
+interface ToastOptions {
+  title?: string;
+  duration?: number;
+}
+
+export function useToast() {
+  const { addToast, removeToast, clearToasts } = useToastStore();
+
+  const toast = useCallback(
+    (type: ToastType, message: string, options?: ToastOptions) => {
+      return addToast({
+        type,
+        message,
+        title: options?.title,
+        duration: options?.duration ?? DEFAULT_DURATION,
+      });
+    },
+    [addToast]
+  );
+
+  const success = useCallback(
+    (message: string, options?: ToastOptions) => toast('success', message, options),
+    [toast]
+  );
+
+  const error = useCallback(
+    (message: string, options?: ToastOptions) => toast('error', message, options),
+    [toast]
+  );
+
+  const warning = useCallback(
+    (message: string, options?: ToastOptions) => toast('warning', message, options),
+    [toast]
+  );
+
+  const info = useCallback(
+    (message: string, options?: ToastOptions) => toast('info', message, options),
+    [toast]
+  );
+
+  const dismiss = useCallback(
+    (id: string) => removeToast(id),
+    [removeToast]
+  );
+
+  const dismissAll = useCallback(() => clearToasts(), [clearToasts]);
+
+  return {
+    toast,
+    success,
+    error,
+    warning,
+    info,
+    dismiss,
+    dismissAll,
+  };
+}
+
+export type { ToastOptions };
diff --git a/web/src/layouts/AdminLayout.tsx b/web/src/layouts/AdminLayout.tsx
index 4b16a6f..649af68 100644
--- a/web/src/layouts/AdminLayout.tsx
+++ b/web/src/layouts/AdminLayout.tsx
@@ -27,9 +27,14 @@ import {
   BookOpen,
   Gauge,
   CalendarDays,
+  CreditCard,
+  Wallet,
+  PiggyBank,
+  ArrowLeftRight,
 } from 'lucide-react';
 import clsx from 'clsx';
 import { useAuthStore } from '../stores/authStore';
+import { ThemeToggle } from '../components/theme';
 
 interface NavItem {
   label: string;
@@ -100,6 +105,18 @@ const navSections: NavSection[] = [
       { label: 'Inspecciones', href: '/admin/hse/inspecciones', icon: ClipboardCheck },
     ],
   },
+  {
+    title: 'Finanzas',
+    defaultOpen: false,
+    items: [
+      { label: 'Flujo de Efectivo', href: '/admin/finanzas/flujo-efectivo', icon: ArrowLeftRight },
+      { label: 'Cuentas por Cobrar', href: '/admin/finanzas/cxc', icon: Wallet },
+      { label: 'Cuentas por Pagar', href: '/admin/finanzas/cxp', icon: CreditCard },
+      { label: 'Facturas', href: '/admin/finanzas/facturas', icon: Receipt },
+      { label: 'Pólizas', href: '/admin/finanzas/polizas', icon: FileText },
+      { label: 'Cuentas Contables', href: '/admin/finanzas/cuentas', icon: PiggyBank },
+    ],
+  },
 ];
 
 export function AdminLayout() {
@@ -132,11 +149,11 @@ export function AdminLayout() {
   };
 
   return (
-    <div className="min-h-screen bg-gray-100">
+    <div className="min-h-screen bg-background-subtle dark:bg-background transition-colors duration-200">
       {/* Mobile sidebar backdrop */}
       {sidebarOpen && (
         <div
-          className="fixed inset-0 bg-gray-600 bg-opacity-75 z-20 lg:hidden"
+          className="fixed inset-0 bg-foreground/50 dark:bg-black/70 z-20 lg:hidden"
           onClick={() => setSidebarOpen(false)}
         />
       )}
@@ -144,17 +161,17 @@ export function AdminLayout() {
       {/* Sidebar */}
       <aside
         className={clsx(
-          'fixed inset-y-0 left-0 z-30 w-64 bg-white shadow-lg transform transition-transform duration-300 lg:translate-x-0 lg:static',
+          'fixed inset-y-0 left-0 z-30 w-64 bg-surface-card dark:bg-surface-card shadow-lg transform transition-all duration-300 lg:translate-x-0 lg:static',
           sidebarOpen ? 'translate-x-0' : '-translate-x-full'
         )}
       >
-        <div className="flex items-center justify-between h-16 px-4 border-b">
+        <div className="flex items-center justify-between h-16 px-4 border-b border-border dark:border-border">
           <Link to="/admin" className="flex items-center space-x-2">
-            <Building2 className="w-8 h-8 text-blue-600" />
-            <span className="text-xl font-bold text-gray-900">ERP Construccion</span>
+            <Building2 className="w-8 h-8 text-primary" />
+            <span className="text-xl font-bold text-foreground">ERP Construccion</span>
           </Link>
           <button
-            className="lg:hidden p-2 rounded-md text-gray-500 hover:bg-gray-100"
+            className="lg:hidden p-2 rounded-md text-foreground-muted hover:bg-background-muted dark:hover:bg-background-emphasis"
             onClick={() => setSidebarOpen(false)}
           >
             <X className="w-5 h-5" />
@@ -172,7 +189,9 @@ export function AdminLayout() {
                   onClick={() => toggleSection(section.title)}
                   className={clsx(
                     'flex items-center justify-between w-full px-3 py-2 text-xs font-semibold uppercase tracking-wider rounded-lg transition-colors',
-                    isActive ? 'text-blue-700 bg-blue-50' : 'text-gray-500 hover:bg-gray-50'
+                    isActive
+                      ? 'text-primary bg-primary/10 dark:bg-primary/20'
+                      : 'text-foreground-muted hover:bg-background-muted dark:hover:bg-background-emphasis'
                   )}
                 >
                   {section.title}
@@ -195,8 +214,8 @@ export function AdminLayout() {
                             className={clsx(
                               'flex items-center px-3 py-2 rounded-lg transition-colors text-sm',
                               isItemActive
-                                ? 'bg-blue-100 text-blue-700 font-medium'
-                                : 'text-gray-700 hover:bg-gray-100'
+                                ? 'bg-primary/10 text-primary dark:bg-primary/20 font-medium'
+                                : 'text-foreground hover:bg-background-muted dark:hover:bg-background-emphasis'
                             )}
                           >
                             <Icon className="w-4 h-4 mr-3" />
@@ -216,36 +235,42 @@ export function AdminLayout() {
       {/* Main content */}
       <div className="lg:pl-64">
         {/* Top bar */}
-        <header className="sticky top-0 z-10 bg-white shadow-sm">
+        <header className="sticky top-0 z-10 bg-surface-card dark:bg-surface-card shadow-sm border-b border-border dark:border-border">
           <div className="flex items-center justify-between h-16 px-4">
             <button
-              className="lg:hidden p-2 rounded-md text-gray-500 hover:bg-gray-100"
+              className="lg:hidden p-2 rounded-md text-foreground-muted hover:bg-background-muted dark:hover:bg-background-emphasis"
               onClick={() => setSidebarOpen(true)}
+              aria-label="Abrir menú"
             >
               <Menu className="w-6 h-6" />
             </button>
 
             <div className="flex-1" />
 
+            {/* Theme toggle */}
+            <ThemeToggle simple size="md" className="mr-2" />
+
             {/* User menu */}
             <div className="relative">
               <button
-                className="flex items-center space-x-2 p-2 rounded-lg hover:bg-gray-100"
+                className="flex items-center space-x-2 p-2 rounded-lg hover:bg-background-muted dark:hover:bg-background-emphasis transition-colors"
                 onClick={() => setUserMenuOpen(!userMenuOpen)}
+                aria-label="Menú de usuario"
+                aria-expanded={userMenuOpen}
               >
-                <div className="w-8 h-8 bg-blue-100 rounded-full flex items-center justify-center">
-                  <User className="w-5 h-5 text-blue-600" />
+                <div className="w-8 h-8 bg-primary/10 dark:bg-primary/20 rounded-full flex items-center justify-center">
+                  <User className="w-5 h-5 text-primary" />
                 </div>
-                <span className="hidden sm:block text-sm font-medium text-gray-700">
+                <span className="hidden sm:block text-sm font-medium text-foreground">
                   {user?.firstName || user?.email || 'Usuario'}
                 </span>
-                <ChevronDown className="w-4 h-4 text-gray-500" />
+                <ChevronDown className="w-4 h-4 text-foreground-muted" />
               </button>
 
               {userMenuOpen && (
-                <div className="absolute right-0 mt-2 w-48 bg-white rounded-lg shadow-lg border py-1">
+                <div className="absolute right-0 mt-2 w-48 bg-surface-popover dark:bg-surface-popover rounded-lg shadow-lg border border-border py-1 z-dropdown">
                   <button
-                    className="flex items-center w-full px-4 py-2 text-sm text-gray-700 hover:bg-gray-100"
+                    className="flex items-center w-full px-4 py-2 text-sm text-foreground hover:bg-background-muted dark:hover:bg-background-emphasis transition-colors"
                     onClick={handleLogout}
                   >
                     <LogOut className="w-4 h-4 mr-2" />
diff --git a/web/src/stores/themeStore.ts b/web/src/stores/themeStore.ts
new file mode 100644
index 0000000..409300f
--- /dev/null
+++ b/web/src/stores/themeStore.ts
@@ -0,0 +1,100 @@
+/**
+ * Theme Store
+ * Gestión del tema (light/dark/system) con persistencia
+ */
+
+import { create } from 'zustand';
+import { persist } from 'zustand/middleware';
+
+export type Theme = 'light' | 'dark' | 'system';
+
+interface ThemeState {
+  theme: Theme;
+  resolvedTheme: 'light' | 'dark';
+  setTheme: (theme: Theme) => void;
+  toggleTheme: () => void;
+}
+
+/**
+ * Resuelve el tema actual basado en la preferencia del sistema
+ */
+const getSystemTheme = (): 'light' | 'dark' => {
+  if (typeof window === 'undefined') return 'light';
+  return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
+};
+
+/**
+ * Resuelve el tema efectivo
+ */
+const resolveTheme = (theme: Theme): 'light' | 'dark' => {
+  if (theme === 'system') {
+    return getSystemTheme();
+  }
+  return theme;
+};
+
+/**
+ * Aplica el tema al documento
+ */
+const applyTheme = (resolvedTheme: 'light' | 'dark') => {
+  if (typeof document === 'undefined') return;
+
+  const root = document.documentElement;
+
+  if (resolvedTheme === 'dark') {
+    root.classList.add('dark');
+    root.setAttribute('data-theme', 'dark');
+  } else {
+    root.classList.remove('dark');
+    root.setAttribute('data-theme', 'light');
+  }
+};
+
+export const useThemeStore = create<ThemeState>()(
+  persist(
+    (set, get) => ({
+      theme: 'system',
+      resolvedTheme: getSystemTheme(),
+
+      setTheme: (theme: Theme) => {
+        const resolvedTheme = resolveTheme(theme);
+        applyTheme(resolvedTheme);
+        set({ theme, resolvedTheme });
+      },
+
+      toggleTheme: () => {
+        const { theme } = get();
+        const newTheme: Theme = theme === 'light' ? 'dark' : 'light';
+        const resolvedTheme = resolveTheme(newTheme);
+        applyTheme(resolvedTheme);
+        set({ theme: newTheme, resolvedTheme });
+      },
+    }),
+    {
+      name: 'erp-construccion-theme',
+      partialize: (state) => ({ theme: state.theme }),
+      onRehydrateStorage: () => (state) => {
+        // Aplicar tema al rehidratar desde localStorage
+        if (state) {
+          const resolvedTheme = resolveTheme(state.theme);
+          applyTheme(resolvedTheme);
+          state.resolvedTheme = resolvedTheme;
+        }
+      },
+    }
+  )
+);
+
+// Listener para cambios en preferencia del sistema
+if (typeof window !== 'undefined') {
+  const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)');
+
+  mediaQuery.addEventListener('change', (e) => {
+    const state = useThemeStore.getState();
+    if (state.theme === 'system') {
+      const resolvedTheme = e.matches ? 'dark' : 'light';
+      applyTheme(resolvedTheme);
+      useThemeStore.setState({ resolvedTheme });
+    }
+  });
+}
diff --git a/web/src/stores/toastStore.ts b/web/src/stores/toastStore.ts
new file mode 100644
index 0000000..1e10f81
--- /dev/null
+++ b/web/src/stores/toastStore.ts
@@ -0,0 +1,46 @@
+/**
+ * Toast Store - Global state for toast notifications
+ */
+
+import { create } from 'zustand';
+
+export type ToastType = 'success' | 'error' | 'warning' | 'info';
+
+export interface Toast {
+  id: string;
+  type: ToastType;
+  message: string;
+  title?: string;
+  duration?: number;
+}
+
+interface ToastState {
+  toasts: Toast[];
+  addToast: (toast: Omit<Toast, 'id'>) => string;
+  removeToast: (id: string) => void;
+  clearToasts: () => void;
+}
+
+let toastId = 0;
+
+export const useToastStore = create<ToastState>((set) => ({
+  toasts: [],
+
+  addToast: (toast) => {
+    const id = `toast-${++toastId}`;
+    set((state) => ({
+      toasts: [...state.toasts, { ...toast, id }],
+    }));
+    return id;
+  },
+
+  removeToast: (id) => {
+    set((state) => ({
+      toasts: state.toasts.filter((t) => t.id !== id),
+    }));
+  },
+
+  clearToasts: () => {
+    set({ toasts: [] });
+  },
+}));