refactor: migrate to template-based theme system, clean up old per-theme configs

- Remove per-theme app configs (alacritty, foot, ghostty, hyprland,
  hyprlock, mako, rofi, swayosd, tmux, walker, waybar, etc.) now
  handled by default/themed/ templates
- Update omarchy scripts (bg-next, list, set) for new template flow
- Update configs: bootstrap, nvim, rofi, tmux, mako
- Tweak installers (02-install-base.sh, btop, desktop, goose, nvim,
  obsidian, theme, tmux)
- Remove obsolete hyprland-rofi-* and hyprland-walker-* scripts
- Update neovim.lua across remaining themes

themes/catppuccin/btop.theme

@@ -1,5 +1,5 @@
 # Main background, empty for terminal default, need to be empty if you want transparent background
-theme[main_bg]="#24273a"
+theme[main_bg]="#1E1E2E"
 
 # Main text color
 theme[main_fg]="#c6d0f5"