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