Refactor item management: Update schemas, models, and API routes

- Renamed customs-related schemas in line_items to LineCustomCreate, LineCustomUpdate, and LineCustomResponse.
- Adjusted models to streamline invoice_id mapping in Item model.
- Enhanced item routes to include company_id in summary statistics endpoint.
- Refactored ItemService to improve item creation and update logic, removing redundant methods.
- Updated frontend components for item management, including new item creation and editing functionalities.
- Added API client for items with CRUD operations and improved error handling.

backend/api/v1/modules/a76/router.py

@@ -9,6 +9,7 @@ from .customs_brokers.routes import router as customs_broker_router
 
 # Importar routers de módulos
 from .invoices.routes import router as invoices_router
+from .items.routes import router as items_router
 from .classes import router as classes_router
 from .clients_and_providers import router as client_and_provider_router
 from .general_catalogs.company import router as company_router
@@ -46,6 +47,7 @@ router = APIRouter()
 
 # Registrar módulos
 router.include_router(invoices_router, prefix="/a76", tags=["a76 / invoices"])
+router.include_router(items_router, prefix="/a76", tags=["a76 / items"])
 router.include_router(pedimentos_router, prefix="/a76")
 router.include_router(
     client_and_provider_router, prefix="/a76", tags=["a76 / clients_and_providers"]