fix: improve maintenance and synchronize live conversations

backend/app/models/rating.py

@@ -15,7 +15,7 @@ limitations under the License.
 """
 
 import uuid
-from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime
+from sqlalchemy import Column, Integer, Text, ForeignKey, DateTime
 from sqlalchemy.orm import relationship
 from sqlalchemy.dialects.postgresql import UUID
 from app.database import Base