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

installer/theme.sh

@@ -18,8 +18,7 @@ ${DOTFILES_DIR}/sync-script script/omarchy-theme-list
 ${DOTFILES_DIR}/sync-script script/omarchy-theme-set
 
 # Set initial theme
-THEMES_DIR="$HOME/.local/share/themes"
-mkdir -p ${THEMES_DIR}
-ln -snf  ${DOTFILES_DIR}/themes/ ${THEMES_DIR}/available
+THEME_DIR="${HOME}/.config/omarchy/current/theme"
+mkdir -p ${THEME_DIR}
 omarchy-theme-set "tokyo-night"