This commit addresses several issues related to encrypted drive handling during application shutdown and provides better user feedback.
- **Fix(GUI):** Prevent `bgerror` by cancelling pending `_process_queue` calls when the application is closing.
- **Feat(Unmount):** Implement logic to prevent application closure if encrypted drives fail to unmount gracefully. A `MessageDialog` is now displayed to the user in such cases.
- **Feat(UI):** Enhance `HeaderFrame` to display the current mount status of encrypted drives, providing immediate visual feedback.
- **Fix(Syntax):** Correct `SyntaxError: unterminated f-string literal` in `encryption_manager.py` by using triple-quoted f-strings for multi-line content.
- **Fix(Translation):** Add missing translation strings (`unmount_failed_title`, `unmount_failed_message`) to `core/pbp_app_config.py`.
- **Fix(Unmount):** Remove `|| true` from shell commands in `unmount_and_reset_owner` to ensure actual unmount failures are correctly reported and handled by the application logic.