[GAP-001] fix: Add explicit varchar type to KpiConfig.category column

TypeORM requires explicit type annotation for union type columns.
Without it, TypeORM inferred 'Object' which is not a valid PostgreSQL type.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/modules/reports/entities/kpi-config.entity.ts

@@ -59,7 +59,7 @@ export class KpiConfig {
   description?: string;
 
   // Clasificacion
-  @Column({ length: 50 })
+  @Column({ type: 'varchar', length: 50 })
   category!: KpiCategory;
 
   @Column({ length: 50 })