Fix bos-settings compile errors and use REGISTRY_TOKEN for publishing

bos-settings was scaffolded but never compiled. Fixes:
- main.rs: import gtk4::prelude (connect_activate/run)
- window.rs: disambiguate WidgetExt::display(); drop unused GBox import
- hyprland.rs: Label has no set_monospace -> use the monospace CSS class
- theme.rs: drop unused prelude import

Also switch package.yml to secrets.REGISTRY_TOKEN (scoped write:package),
since the auto Actions token is not authorized for the owner registry.

bos-settings/src/ui/window.rs

@@ -1,5 +1,5 @@
 use gtk4::prelude::*;
-use gtk4::{Application, ApplicationWindow, Box as GBox, Orientation, Paned, Stack};
+use gtk4::{Application, ApplicationWindow, Orientation, Paned, Stack};
 
 use super::sidebar;
 use super::views;
@@ -12,7 +12,7 @@ pub fn build_ui(app: &Application) {
         .default_height(640)
         .build();
 
-    crate::theme::load(&window.display());
+    crate::theme::load(&WidgetExt::display(&window));
 
     let hpaned = Paned::new(Orientation::Horizontal);
     hpaned.set_position(190);