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/neovim.lua

@@ -1,11 +1,13 @@
 return {
-    {
-        "catppuccin/nvim",
-        name = "catppuccin",
-        lazy = false,
-        priority = 1000,
-        config = function()
-            vim.cmd("colorscheme catppuccin")
-        end,
+  {
+    "catppuccin/nvim",
+    name = "catppuccin",
+    priority = 1000,
+  },
+  {
+    "LazyVim/LazyVim",
+    opts = {
+      colorscheme = "catppuccin-nvim",
     },
+  },
 }