[LyX/master] Fix dark/light mode setting and run-time switch with Qt 6.8

[Jürgen Spitzmüller]

Am Montag, dem 21.10.2024 um 20:52 +0200 schrieb Yu Jin:
> Can you help me out? What exactly do I need to test here? 

A runtime switch of (dark/light) mode should work now. At least there
should be no drawbacks as far as dark/light mode setting on Windows are
concerned.

> Does it correlate with #12224? 

Yes, but that adds an extra feature.



-- 
Jürgen