refactor: migrate models to canonical module locations

- Move Product/ProductTranslation to app/modules/catalog/models/
- Move VendorOnboarding to app/modules/marketplace/models/
- Delete legacy re-export files for marketplace models:
  - letzshop.py, marketplace.py, marketplace_product.py
  - marketplace_product_translation.py, marketplace_import_job.py
- Delete legacy product.py, product_translation.py, onboarding.py
- Update all imports across services, tasks, tests to use module locations

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

app/modules/analytics/services/stats_service.py

@@ -21,10 +21,9 @@ from sqlalchemy.orm import Session
 from app.exceptions import AdminOperationException, VendorNotFoundException
 from app.modules.customers.models.customer import Customer
 from app.modules.inventory.models import Inventory
-from models.database.marketplace_import_job import MarketplaceImportJob
-from models.database.marketplace_product import MarketplaceProduct
+from app.modules.marketplace.models import MarketplaceImportJob, MarketplaceProduct
 from app.modules.orders.models import Order
-from models.database.product import Product
+from app.modules.catalog.models import Product
 from models.database.user import User
 from models.database.vendor import Vendor
 

app/modules/analytics/services/usage_service.py

@@ -16,7 +16,7 @@ from dataclasses import dataclass
 from sqlalchemy import func
 from sqlalchemy.orm import Session
 
-from models.database.product import Product
+from app.modules.catalog.models import Product
 from models.database.subscription import SubscriptionTier, VendorSubscription
 from models.database.vendor import VendorUser