waybar: use catppuccin module, add GTK theme

Switch waybar from manual fetchFromGitHub theme to catppuccin/nix module.
Add catppuccin macchiato GTK theme to fix unreadable tray context menus.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

home/hosts/gunter/default.nix

@@ -23,6 +23,7 @@
           ../../packages
           ../../programs/dunst
           ../../programs/git
+          ../../programs/gtk
           ../../programs/firefox
           ../../programs/kitty
           ../../programs/obs-studio

home/hosts/magicman/default.nix

@@ -26,6 +26,7 @@
           ../../programs/tmux
           ../../programs/dunst
           ../../programs/kitty
+          ../../programs/gtk
           ../../programs/rofi
           ../../programs/obs-studio
           ../../programs/vscode