feat: payments module, notification templates, WA float, route fixes

- Add PaymentsModule: POST /payments/intent, POST /:id/confirm, GET /payments, GET /payments/package/:id, GET /payments/track/:trackingId
- Add Payment model to Prisma schema (PaymentStatus enum, Payment table)
- Add NotificationTemplate model + NotificationsController (GET/PUT /notification-templates, POST /notification-templates/seed)
- Update NotificationsService: DB-backed templates with variable interpolation {{trackingId}} {{firstName}} {{status}} {{suiteCode}}
- Fix /bodega/paquetes: replace 11 wrong status strings with correct §08 enum values
- Fix /admin/reportes: replace EN_CAMINO_A_ECUADOR with correct §08 statuses, rewrite report page with proper KPIs and bar charts
- Fix /portal/mis-paquetes: correct §08 statuses, add 'Pagar envío' button for VERIFICADO/DECLARACION_ADUANERA packages
- Add WhatsApp float component (_components/whatsapp-float.tsx, 2 contacts: NJ ops + Cuenca aduana)
- Add /casillero/calculadora and /casillero/registro redirects (§20)
- Add /portal/pago payment page with cost breakdown (§09/§14/§15)
- Add /admin/notificaciones page: view/edit/toggle templates per event×channel
- Admin nav: add Notificaciones link
- api.ts: add notificationTemplates.* and payments.* client methods
- schema.prisma v0.4: PaymentStatus enum, Payment model, NotificationTemplate model
- db push applied to remote DB (46.202.93.92)
- All builds pass (API nest build + Next.js build)

apps/api/src/app.module.ts

@@ -16,6 +16,7 @@ import { TariffsModule } from "./tariffs/tariffs.module";
 import { ProductsModule } from "./products/products.module";
 import { WarehousesModule } from "./warehouses/warehouses.module";
 import { IntegrationsModule } from "./integrations/integrations.module";
+import { PaymentsModule } from "./payments/payments.module";
 
 @Module({
   imports: [
@@ -39,6 +40,7 @@ import { IntegrationsModule } from "./integrations/integrations.module";
     ProductsModule,
     WarehousesModule,
     IntegrationsModule,
+    PaymentsModule,
   ],
 })
 export class AppModule {}