Add missing session.add(flow) to ensure flow is added to the session …

…before commit

src/backend/base/langflow/services/database/service.py

@@ -187,6 +187,7 @@ async def assign_orphaned_flows_to_superuser(self) -> None:
                 flow.user_id = superuser.id
                 flow.name = self._generate_unique_flow_name(flow.name, existing_names)
                 existing_names.add(flow.name)
+                session.add(flow)
 
             # Commit changes
             await session.commit()