theme: GTK and Qt take the YoRHa palette

GTK moves from Catppuccin Mocha to adw-gtk3-dark, recoloured through the
libadwaita named colours in gtk-3.0/gtk.css and as CSS variables in
gtk-4.0/gtk.css, so Nautilus and other libadwaita apps follow too. The
gtk-4.0 symlinks into the Catppuccin theme are gone, since libadwaita
would load its gtk-dark.css over the overrides.

Qt gets qt6ct/colors/yorha.conf: the same palette in QPalette roles,
with the light slab as the highlight and ink as its text.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

xsettingsd/xsettingsd.conf

@@ -1,4 +1,4 @@
-Net/ThemeName "catppuccin-mocha-blue-standard+default"
+Net/ThemeName "adw-gtk3-dark"
 Net/IconThemeName "Papirus-Dark"
 Gtk/CursorThemeName "Bibata-Modern-Classic"
 Net/EnableEventSounds 1