feat(settings): default close_to_tray in settings store

src/lib/stores/settings.svelte.ts

@@ -49,6 +49,7 @@ const DEFAULT_SETTINGS: AppSettings = {
   microphone_enabled: true, // capture the user's mic into the transcript (FR-CAP-7)
   audio_input_device: null, // system default capture device
   auto_start: false, // launch at login — opt-in, off by default (NFR-RES-4)
+  close_to_tray: true, // closing the window hides to tray; on by default
 };
 
 class SettingsStore {