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/gruvbox/neovim.lua

@@ -1,14 +1,9 @@
 return {
-    { 
-        "ellisonleao/gruvbox.nvim", 
-        lazy = false,
-        priority = 1000,
-        config = function ()
-            require("gruvbox").setup({
-                contrast = "hard",
-                transparent_mode = true,
-            })
-            vim.cmd("colorscheme gruvbox")
-        end,
-    },
+	{ "ellisonleao/gruvbox.nvim" },
+	{
+		"LazyVim/LazyVim",
+		opts = {
+			colorscheme = "gruvbox",
+		},
+	},
 }