feat: add minimize to system tray option

Add ability to minimize Hikari to the system tray when closing the window
instead of fully exiting. When enabled, clicking the close button hides
the window and shows a tray icon with "Show Hikari" and "Quit" options.

- Add tray module with system tray setup and menu handling
- Add minimize_to_tray config option in settings
- Handle window close event to hide instead of close when enabled
- Add tray icon click handler to restore window

src/lib/components/StatusBar.svelte

@@ -49,6 +49,7 @@
     update_checks_enabled: true,
     character_panel_width: null,
     font_size: 14,
+    minimize_to_tray: false,
   });
 
   onMount(async () => {