refactor(ban_service): extract _bans_by_country_load_data helper

Break up long function into focused helper. Load data logic separate from aggregation.

backend/app/utils/config_file_utils.py

@@ -2,6 +2,7 @@ from __future__ import annotations
 
 import asyncio
 import configparser
+import contextlib
 import io
 import os
 import re