fix: improve maintenance and synchronize live conversations

backend/app/repositories/workflow.py

@@ -14,14 +14,11 @@ See the License for the specific language governing permissions and
 limitations under the License.
 """
 
-from typing import List, Optional, Dict, Any
+from typing import List, Optional
 from uuid import UUID
 from sqlalchemy.orm import Session, selectinload
-from sqlalchemy.exc import SQLAlchemyError
 
 from app.models.workflow import Workflow, WorkflowStatus
-from app.models.workflow_node import WorkflowNode
-from app.models.workflow_connection import WorkflowConnection
 
 from app.core.logger import get_logger