feat: add import error tracking and translation tabs

Import Error Tracking:
- Add MarketplaceImportError model to store detailed error information
- Store row number, identifier, error type, message, and row data for each error
- Add API endpoint GET /admin/marketplace-import-jobs/{job_id}/errors
- Add UI to view and browse import errors in job details modal
- Support pagination and error type filtering

Translation Tabs:
- Replace flat translation list with tabbed interface on product detail page
- Add language tabs with full language names
- Add copy-to-clipboard functionality for translation content
- Improved UX with better visual separation of translations

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/integration/api/v1/admin/test_letzshop.py

@@ -189,7 +189,7 @@ class TestAdminLetzshopCredentialsAPI:
 class TestAdminLetzshopConnectionAPI:
     """Test admin Letzshop connection testing endpoints."""
 
-    @patch("app.services.letzshop.client.requests.Session.post")
+    @patch("app.services.letzshop.client_service.requests.Session.post")
     def test_test_vendor_connection(
         self, mock_post, client, admin_headers, test_vendor
     ):
@@ -217,7 +217,7 @@ class TestAdminLetzshopConnectionAPI:
         data = response.json()
         assert data["success"] is True
 
-    @patch("app.services.letzshop.client.requests.Session.post")
+    @patch("app.services.letzshop.client_service.requests.Session.post")
     def test_test_api_key_directly(
         self, mock_post, client, admin_headers
     ):
@@ -287,7 +287,7 @@ class TestAdminLetzshopOrdersAPI:
         assert data["total"] == 1
         assert data["orders"][0]["customer_email"] == "admin-test@example.com"
 
-    @patch("app.services.letzshop.client.requests.Session.post")
+    @patch("app.services.letzshop.client_service.requests.Session.post")
     def test_trigger_vendor_sync(
         self, mock_post, client, admin_headers, test_vendor
     ):