fix: improve maintenance and synchronize live conversations

backend/app/models/chat_history.py

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 """
 
-from sqlalchemy import Column, Integer, String, JSON, ForeignKey, TIMESTAMP, func, UUID, Interval, Float, Index, text
+from sqlalchemy import Column, Integer, String, JSON, ForeignKey, TIMESTAMP, func, UUID, Float, Index, text
 from sqlalchemy.orm import relationship
 from app.core.encryption import EncryptedText
 from app.database import Base