* KDE theme: fix visual problems with KDE dark mode; add system theme
* Make "Light" theme truly light under Breeze Dark theme.
* With this fix also expose dark mode support on Windows.
* Add "Auto" (system) theme that follows system style and color.
* Add "Adaptive" color scheme for system theme (using transparent background).
* Add support for transparent background in color schemes.
* move `alphaBlend` to utils
* hide Auto (system) theme on Windows
Cyano Hao