feat: add omarchy theme template system with management scripts

- New default/themed/ templates (alacritty, btop, foot, ghostty, helix,
  hyprland, hyprlock, kitty, mako, obsidian, rofi, swayosd, tmux,
  walker, waybar, keyboard.rgb, gum.env, etc.)
- Add omarchy-* theme management scripts (install, refresh, set, remove,
  update, bg-set, colors-from-alacritty, current, etc.)
- Add omarchy restart/hook scripts (btop, hyprctl, hypridle, mako, tmux)
- Add installer/environment.sh for shared env vars
- Add 19 theme directories with colors.toml, vscode.json, backgrounds,
  and app-specific configs (catppuccin, everforest, gruvbox, nord,
  tokyo-night, rose-pine, etc.)
- Update bing-wallpaper script to use new .config/omarchy path

script/omarchy-theme-update

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+# omarchy:summary=Update user-installed git themes
+
+for dir in ~/.config/omarchy/themes/*/; do
+  if [[ -d $dir ]] && [[ ! -L ${dir%/} ]] && [[ -d $dir/.git ]]; then
+    echo "Updating: $(basename "$dir")"
+    git -C "$dir" pull
+  fi
+done