feat(crm): módulo Tarifario — modelos, CRUD, import Excel y motor de costeo

- Tablas rate_sheets/lanes/breaks/charges (esquema crm) + migración con down().
- Catálogos nuevos: modo_tarifario, unidad_tarifa, concepto_cargo.
- CRUD de tarifarios y rutas; descarga de plantilla Excel por modo; import con
  vista previa y validación; alta directa desde Excel.
- Motor de costeo /rate-quote: aéreo (peso facturable + quiebres + optimización),
  marítimo FCL (por contenedor), LCL (W/M) y terrestre; suma cargos adicionales.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/api/v1/modules/crm/router.py

@@ -21,6 +21,8 @@ from .metrics.routes import router as metrics_router
 from .opportunities.routes import router as opportunities_router
 from .pipelines.routes import router as pipelines_router
 from .quotes.routes import router as quotes_router
+from .rates.routes import cost_router as rates_cost_router
+from .rates.routes import router as rates_router
 from .service_requests.routes import router as service_requests_router
 from .suppliers.routes import router as suppliers_router
 from .uploads.routes import router as uploads_router
@@ -44,3 +46,5 @@ router.include_router(activities_router)
 router.include_router(metrics_router)
 router.include_router(catalogs_router)
 router.include_router(uploads_router)
+router.include_router(rates_router)
+router.include_router(rates_cost_router)