Move Fail2Ban exceptions into central app.exceptions module

backend/tests/test_routers/test_bans.py

@@ -13,7 +13,7 @@ from app.config import Settings
 from app.db import init_db
 from app.main import create_app
 from app.models.ban import ActiveBan, ActiveBanListResponse
-from app.utils.fail2ban_client import Fail2BanConnectionError
+from app.exceptions import Fail2BanConnectionError
 
 # ---------------------------------------------------------------------------
 # Fixtures