feat(launcher): implement Phase 5 system management UI and relay

- Expose new native handlers in electron_relay.ts (Wallpaper, Updates, Window Control, Power).
- Overhaul Native OS Management UI with controls for window states, display layouts, and power.
- Add Application Updates component with support for local and web sources.
- Include confirmation modal for dangerous system actions (shutdown/reboot).
- Update TODO.md to mark Phase 5 integration as completed.

src/routes/events/[event_id]/(launcher)/launcher_cfg.svelte

@@ -27,6 +27,7 @@
     import LauncherCfgNativeOS from './cfg_components/launcher_cfg_native_os.svelte';
     import LauncherCfgSyncTimers from './cfg_components/launcher_cfg_sync_timers.svelte';
     import LauncherCfgHealth from './cfg_components/launcher_cfg_health.svelte';
+    import LauncherCfgUpdates from './cfg_components/launcher_cfg_updates.svelte';
     import LauncherCfgController from './cfg_components/launcher_cfg_controller.svelte';
     import LauncherCfgScreenSaver from './cfg_components/launcher_cfg_screen_saver.svelte';
     import LauncherCfgAppModes from './cfg_components/launcher_cfg_app_modes.svelte';
@@ -58,6 +59,7 @@
         <LauncherCfgNativeOS />
         <LauncherCfgSyncTimers />
         <LauncherCfgHealth />
+        <LauncherCfgUpdates />
     {/if}
 
     <LauncherCfgController />