Refactor history sync into history_service and update docs/tests

backend/app/services/server_service.py

@@ -14,7 +14,6 @@ from typing import cast
 
 import structlog
 
-from app.exceptions import ServerOperationError
 from app.exceptions import ServerOperationError
 from app.models.server import ServerSettings, ServerSettingsResponse, ServerSettingsUpdate
 from app.utils.fail2ban_client import Fail2BanClient, Fail2BanCommand, Fail2BanResponse