Add manual “Black Screen” button during foreground backup to reduce OLED burn-in, heat, and battery usage

I have searched the existing feature requests, both open and closed, to make sure this is not a duplicate request. • Yes The feature Please add a manual button on the foreground backup screen to switch the display to a fully black screen while backup continues. This is useful during large backups on OLED devices to reduce battery usage, heat, and screen wear. Requirements • user taps a button to enable it • backup continues normally in the foreground • device stays awake • screen becomes completely black • no persistent UI, text, progress, or overlays visible • show only a brief toast when enabling it or when touching the screen, for example: “Black screen enabled. Double tap anywhere to exit.” • exit by double tapping the screen • after exit, return to the normal backup UI This should be a manual, opt-in mode, not automatic dimming or automatic black-screen behavior. Thanks :) Platform • Server …