🔥(backend) remove useless imports from backend code

Clean up unused imports in backend modules as minor maintenance work
not related to current PR.

src/backend/core/recording/event/authentication.py

@@ -4,7 +4,6 @@ import logging
 import secrets
 
 from django.conf import settings
-from django.utils.translation import gettext_lazy as _
 
 from rest_framework.authentication import BaseAuthentication
 from rest_framework.exceptions import AuthenticationFailed