Share what's playing in any Android music app

A local Expo module listens to system media sessions (the only way
Android exposes other apps' playback, gated by notification access; we
never read notifications). It filters to known music apps, debounces and
deduplicates changes, sends a heartbeat while playing, and delivers
reports through WorkManager so they survive the app being closed.

- One-screen onboarding that doubles as Google Play's prominent
  disclosure, opening straight to the app's toggle in Android settings
- Only media notifications are pre-ticked on that settings screen
- Device registration is single-flight (several screens react to the
  same permission change) and self-heals if the server revokes a token
- Sign-out revokes the phone's token; resuming sharing re-sends the
  current track immediately
- Pause controls in Settings and on the feed
- Fix invisible tab icons and labels on Android
- Keep Metro out of build output so it doesn't exhaust file watchers

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MzFywujuH9TiuXbr9vjoX8

apps/mobile/src/components/NowPlayingCard.tsx

@@ -34,7 +34,7 @@ export function NowPlayingCard({
           {np.isPlaying && <View style={styles.dot} />}
           <Text style={[styles.status, np.isPlaying && { color: colors.live }]} numberOfLines={1}>
             {np.isPlaying ? 'Listening now' : `Played ${timeAgo(np.updatedAt)}`}
-            <Text style={styles.via}> · {SERVICE_LABELS[np.source]}</Text>
+            <Text style={styles.via}> · {np.sourceApp ?? SERVICE_LABELS[np.source]}</Text>
           </Text>
           {onTogglePin && (
             <Pressable