refactor: update module imports to use module locations

Update all module files to import from canonical module locations
instead of legacy re-export files:
- checkout, orders, customers routes: use module schemas
- catalog, marketplace schemas: use inventory module schemas
- marketplace, customers, inventory, analytics services: use module models

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

app/modules/customers/services/customer_service.py

@@ -329,7 +329,7 @@ class CustomerService:
         Raises:
             CustomerNotFoundException: If customer not found
         """
-        from models.database.order import Order
+        from app.modules.orders.models import Order
 
         # Verify customer belongs to vendor
         self.get_customer(db, vendor_id, customer_id)
@@ -365,7 +365,7 @@ class CustomerService:
         """
         from sqlalchemy import func
 
-        from models.database.order import Order
+        from app.modules.orders.models import Order
 
         customer = self.get_customer(db, vendor_id, customer_id)