Add Option for powering off a display in Power Display profiles

### Description of the new feature / enhancement

In the Power Display profiles, you can preset brightness, contrast, and color temperature. Could an option also be added to turn the displays off completely?

### Scenario when this would be used?

You could activate a "cinema mode" with just two mouse clicks that turns off all displays except one. In this case, more screens simply mean more distraction.

### Supporting information

_No response_

No files or tests are named. Start by locating the Power Display profile implementation and how profiles currently apply brightness, contrast, and color temperature; then identify the display power-control entry point. Done means a profile can turn selected displays off while leaving another display on, with the behavior available through the profile UI.

Written by the indexing model from the issue text.