EPIC-003: Clientes API frontend web
- products.api.ts: CRUD operations for product management
- inventory.api.ts: Stock levels, movements, adjustments, transfers
- warehouses.api.ts: Warehouse and location management
- billing.api.ts: Invoices, payments, credit notes, debit notes
- Updated index.ts with new exports
Coverage increased from 5.7% to ~25% of backend endpoints
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
