Add support for changing the lock screen background

[TsofnatMaman]

adding an option to change not only the desktop wallpaper, but also the lock screen background.

Currently, the app focuses on updating the desktop background. It would be useful if users could also enable a setting that applies the background to the Windows lock screen.

Suggested behavior:

• Add an option such as “Apply to lock screen”

• Allow users to choose whether to update:

• Desktop background only

• Lock screen background only
  *Both desktop and lock screen

• Keep the existing desktop background behavior unchanged by default