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

themes/nord/colors.toml

@@ -0,0 +1,23 @@
+accent = "#81a1c1"
+cursor = "#d8dee9"
+foreground = "#d8dee9"
+background = "#2e3440"
+selection_foreground = "#d8dee9"
+selection_background = "#4c566a"
+
+color0 = "#3b4252"
+color1 = "#bf616a"
+color2 = "#a3be8c"
+color3 = "#ebcb8b"
+color4 = "#81a1c1"
+color5 = "#b48ead"
+color6 = "#88c0d0"
+color7 = "#e5e9f0"
+color8 = "#4c566a"
+color9 = "#bf616a"
+color10 = "#a3be8c"
+color11 = "#ebcb8b"
+color12 = "#81a1c1"
+color13 = "#b48ead"
+color14 = "#8fbcbb"
+color15 = "#eceff4"