Light Switch auto-switch desktop background and GPU condition

### Description of the new feature / enhancement

- Change desktop background when Light Switch is triggered
- Change accent color when Light Switch is triggered
- Can also introduce different themes depending on user preference
- Add offset to delay the Light Switch (i.e. offset n minutes before turning on Light switch)
- Add GPU threshold or application condition to not apply Light Switch

### Scenario when this would be used?

1. Prevent user manually changing background/desktop picture whenever dark/light mode is enabled.
2. Delay on triggering Light Switch for user preference.
3. Remove stutters/lag on certain applications and while playing GPU-intensive games.

### Supporting information

_No response_

The issue does not name files, tests, or an entry point. Start by locating the Light Switch implementation and determine which of the requested behaviors belong in one scoped change. Done would require agreed behavior for background, accent or theme changes, delay settings, and GPU or application exclusions, with tests or reproducible checks for the selected scope.

Written by the indexing model from the issue text.