theme: move the alarm colour from pink to mauve

Mocha's pink is a pastel. Filled at slab size against the near-black
Persona surfaces it went chalky rather than sharp, which is what made
hovered destructive buttons read as a washed-out red. Mauve is saturated
enough to bite against that ground and still cannot be confused with the
blue accent.

Applies across quickshell, Hyprland, dunst, fish and nvim. The GTK
overrides are dropped entirely — stock Catppuccin Mocha Blue already
paints those surfaces, and a hand-written destructive colour there was
one more thing to keep in step for no gain.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

gtk-4.0/gtk.css

@@ -2,7 +2,3 @@
  * overrode Fluent's greys with black here; Mocha needs no override — its own
  * surfaces are the palette the rest of the rice is built on. */
 @import url("/usr/share/themes/catppuccin-mocha-blue-standard+default/gtk-4.0/gtk.css");
-
-/* Pink is the shell's alarm colour; keep destructive GTK buttons in step. */
-@define-color destructive_bg_color #f38ba8;
-@define-color destructive_fg_color #11111b;