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.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bos-settings/src/main.rs

@@ -2,6 +2,8 @@ mod config;
 mod theme;
 mod ui;
 
+use gtk4::prelude::*;
+
 fn main() {
     let app = gtk4::Application::builder()
         .application_id("com.breadway.bos-settings")