Refactor logging configuration to use AppData directory

- Updated config.example.json to set default log_file to null.
- Modified config.py to resolve log file paths relative to the AppData directory.
- Added methods to get default log directory and log file path in AppData.
- Ensured logging behavior is consistent whether a log_file is specified or not.

config.example.json

@@ -15,7 +15,7 @@
   "auto_check_updates": true,
   "update_check_interval_hours": 24,
   "log_level": "INFO",
-  "log_file": "logs/webdrop_bridge.log",
+  "log_file": null,
   "window_width": 1024,
   "window_height": 768,
   "enable_logging": true