Fix SQLAlchemy error in sync error handling

- Use already-captured provider name from provider_result dict
- Prevents lazy load attempt on detached object after rollback
- Fixes "MissingGreenlet: greenlet_spawn has not been called" error

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

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

Author: successbyfailure

frontend/api.py

@@ -375,8 +375,8 @@ async def manual_sync(request: Request, session = Depends(get_session)):
                 await session.rollback()
                 provider_result["status"] = "error"
                 provider_result["error"] = str(e)
-                results["errors"].append(f"{provider.name}: {str(e)}")
-                logger.exception(f"Error syncing provider {provider.name}")
+                results["errors"].append(f"{provider_result['name']}: {str(e)}")
+                logger.exception(f"Error syncing provider {provider_result['name']}")
 
             results["providers"].append(provider_result)