Rename noctalia-shell to noctalia and add support

* Rename `nooctalia-plugins` to `noctalia-plugins` in host modules and
  plugin definitions
* Update Hyprland keybindings and exec-once to use the new `noctalia`
  commands
* Add `stylixImage` option and enable pointer cursor in
  `modules/core/user.nix`
* Introduce `modules/home/nixpkgs.nix` to allow unfree packages and
  insecure Electron
* Add full Noctalia configuration module with settings for audio,
  bar, calendar, location, notifications, plugins, shell, wallpaper,
  and widgets
* Enable `noctalia` in `modules/home/stylix.nix` and replace legacy
  `noctalia-shell` imports in `modules/home/default.nix`

modules/home/noctalia/settings/wallpaper.nix

@@ -0,0 +1,12 @@
+{
+  username,
+  stylixImage,
+  ...
+}: let
+  wallpapersPath = "/home/${username}/Pictures/Wallpapers";
+in {
+  programs.noctalia.settings = {
+    lockscreen.wallpaper = "${wallpapersPath}/${stylixImage}";
+    wallpaper.enabled = true;
+  };
+}