Fix internal display toggle not re-applied after resume

[mat-ran]

Problem

When you disable the internal laptop display while an external monitor is connected, then trigger display sleep (screen off) and wake the laptop, the internal display incorrectly turns back on - even though nothing changed with the external monitor connection.
The expected behavior: the internal display should stay disabled after wake, as long as the external monitor remains connected. This works correctly with systemctl suspend, but fails with display sleep.

Root Cause

When the screen turns off (display sleep), the external monitor loses signal due to no input and Hyprland sends a monitorremoved event. Shortly after, when the laptop wakes, the external monitor takes a moment to be detected again. The monitor watcher would immediately try to "recover" the internal display without waiting for the external monitor to reappear on wake, causing a race condition where the internal display gets turned back on before the external monitor is detected.

Solution

1. recover() now waits up to 3 seconds - before re-enabling the internal display, it polls for external monitors to give the system time to detect them on wake
2. Added reapply() function - to properly refresh the toggle state when monitors are reconnected
3. Added monitoradded event handling - ensures toggle state is maintained when monitors are added

Probably fixes #5481

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[dhh]

I tried a few different ways with this and was able to end up with the internal display turned off when I unplugged the external. I think we need some more testing to make sure this is fully solid.

[mat-ran]

I'll check it out. In what situations has the built-in monitor failed to turn on?