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.

src/ui/views/hyprland.rs

@@ -50,7 +50,7 @@ pub fn build() -> GBox {
         for mon in &monitors {
             let lbl = Label::new(Some(mon));
             lbl.set_xalign(0.0);
-            lbl.set_monospace(true);
+            lbl.add_css_class("monospace");
             vbox.append(&lbl);
         }
     }