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/nvim.sh

@@ -8,10 +8,10 @@ ${DOTFILES_DIR}/sync-config config/nvim
 
 # Set specific app links for current theme
 PLUGINS_DIR="${HOME}/.config/nvim/plugin"
-THEMES_DIR="${HOME}/.local/share/themes"
+THEME_DIR="${HOME}/.config/omarchy/current/theme"
 
 mkdir -p ${PLUGINS_DIR}
-ln -snf ${THEMES_DIR}/current/theme/neovim-vimpack.lua ${PLUGINS_DIR}/theme.lua
+ln -snf ${THEME_DIR}/current/theme/neovim-vimpack.lua ${PLUGINS_DIR}/theme.lua
 
 uv tool install vectorcode