[BUG] '--back-to-normal' command fails to restore default wallpaper

When using the '--back-to-normal' command, the application successfully closes the task and removes it from startup apps, but fails to reset the wallpaper to the default one.

Steps to reproduce:
1. Run the application and let it change the wallpaper
2. Execute the command with the '--back-to-normal' flag
3. Observe that the task is removed and startup entry is cleared
4. Notice that the wallpaper remains unchanged, not reverting to the default

Expected behavior:
The '--back-to-normal' command should restore the original default wallpaper.

Actual behavior:
The wallpaper remains set to the last image used by Suppap.

Additional information:
- Operating System: Windows 11
- Python version: 3.12.x

Possible causes to investigate:
- Default wallpaper path retrieval method
- Wallpaper setting mechanism for reverting to default
- Permissions for changing wallpaper
- Windows allow only one wallpaper change in 60 secs (GPT'ed it).