refactor: delete legacy models/database/customer.py

Update the last remaining import in storefront_pages.py to use
app.modules.customers.models, then delete the legacy re-export file.

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

app/routes/storefront_pages.py

@@ -43,7 +43,7 @@ from app.api.deps import get_current_customer_from_cookie_or_header, get_db
 from app.modules.cms.services import content_page_service
 from app.services.platform_settings_service import platform_settings_service
 from app.templates_config import templates
-from models.database.customer import Customer
+from app.modules.customers.models import Customer
 
 router = APIRouter()