fix: improve maintenance and synchronize live conversations

backend/tests/repo/test_file_attachment_repo.py

@@ -15,10 +15,8 @@ limitations under the License.
 """
 
 import pytest
-from datetime import datetime
 from uuid import uuid4
 from app.repositories.file_attachment import FileAttachmentRepository
-from app.models.file_attachment import FileAttachment
 from app.models.chat_history import ChatHistory
 from app.models.customer import Customer
 from app.models.user import User, UserGroup