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/app/(tabs)/_layout.tsx

@@ -6,7 +6,10 @@ export default function TabsLayout() {
     <NativeTabs
       backgroundColor={colors.bg}
       indicatorColor={colors.surface2}
-      labelStyle={{ selected: { color: colors.text } }}
+      // Android defaults icons and labels to black, which vanishes on the dark bar.
+      iconColor={{ default: colors.muted, selected: colors.text }}
+      labelStyle={{ default: { color: colors.muted }, selected: { color: colors.text } }}
+      labelVisibilityMode="labeled"
       tintColor={colors.accent}>
       <NativeTabs.Trigger name="index">
         <NativeTabs.Trigger.Label>Feed</NativeTabs.Trigger.Label>