feat(mobile): sign-in, tabs, search, collection and background player (M5)

- expo-router app in src/app: connect (server check, recent servers),
  login, mandatory credential / password change, tabs Home / Search /
  Collection / Profile, album and artist pages, full-screen player
- AuthSession per server with the refresh token in expo-secure-store
  (Android Keystore); language from the profile
- player on react-native-track-player: ExoPlayer queue with a
  notification and lock-screen controls via a playback service, 500 MB
  stream cache, quality by network (Wi-Fi high, cellular medium),
  play events with played time, reactions, playback state restore and
  the endless My Wave with feedback
- home: pulsing wave circle driven by BPM / energy in the cover
  palette, activity and mood chips that switch the wave on the fly
- New Architecture is off until react-native-track-player supports it;
  the release build runs codegen only when it is on; query-string is a
  direct dependency because expo-router 5.1 imports it undeclared

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/mobile/index.ts

@@ -1,5 +1,9 @@
-import { registerRootComponent } from 'expo';
+// Фоновый сервис плеера регистрируется до запуска UI: кнопки уведомления и гарнитуры
+// работают, даже когда интерфейс выгружен (docs/mobile.md#воспроизведение).
+import TrackPlayer from 'react-native-track-player';
 
-import { App } from './src/App';
+import { PlaybackService } from './src/player/service';
 
-registerRootComponent(App);
+TrackPlayer.registerPlaybackService(() => PlaybackService);
+
+import 'expo-router/entry';