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/hyprland/exec-once.nix

@@ -3,7 +3,7 @@ _: {
     "dbus-update-activation-environment --all --systemd WAYLAND_DISPLAY XDG_CURRENT_DESKTOP"
     "systemctl --user import-environment WAYLAND_DISPLAY XDG_CURRENT_DESKTOP"
     "systemctl --user start hyprpolkitagent"
-    "noctalia-shell"
+    "noctalia"
     "wl-paste --type text --watch cliphist store" # Saves text
     "wl-paste --type image --watch cliphist store" # Saves images
   ];