Connect Apple Music and Spotify-via-Last.fm on iPhone

- Local Expo module (Swift): MusicKit authorization, Music User Token via
  MusicUserTokenProvider, and live Music app now-playing while the app is
  open (MediaPlayer notifications), reported through the device endpoint
- One-tap Apple Music onboarding on iOS; Apple Music row in Settings
- Sign in with Last.fm, plus a guided Spotify-via-Last.fm flow when direct
  Spotify sign-in is capped
- Device registration moved to shared code used by Android and iOS
Not yet compiled for iOS (no Xcode here); needs an EAS build.

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

apps/mobile/src/app/_layout.tsx

@@ -3,9 +3,11 @@ import * as SplashScreen from 'expo-splash-screen';
 import { StatusBar } from 'expo-status-bar';
 import { useEffect } from 'react';
 import { AppState, StyleSheet, View } from 'react-native';
-import { SWRConfig } from 'swr';
+import useSWR, { SWRConfig } from 'swr';
+import type { ConnectionDTO } from '@musicshare/shared';
 import { Body, Button, Title } from '@/components/ui';
 import { api } from '@/lib/api';
+import { appleMusicAvailable, useAppleMusicLive } from '@/lib/appleMusic';
 import { syncDevice } from '@/lib/nowPlayingReader';
 import { SessionProvider, useSession } from '@/lib/session';
 import { colors, space } from '@/lib/theme';
@@ -65,6 +67,7 @@ function AppNavigator() {
           return () => sub.remove();
         },
       }}>
+      {signedIn && appleMusicAvailable && <AppleMusicLive />}
       <Stack
         screenOptions={{
           headerStyle: { backgroundColor: colors.bg },
@@ -86,6 +89,13 @@ function AppNavigator() {
   );
 }
 
+/** iOS: mirror the Music app live while the app is open, once Apple Music is connected. */
+function AppleMusicLive() {
+  const { data: connections } = useSWR<ConnectionDTO[]>('/connections');
+  useAppleMusicLive(Boolean(connections?.some((c) => c.provider === 'apple_music' && c.status === 'active')));
+  return null;
+}
+
 const styles = StyleSheet.create({
   offline: { flex: 1, backgroundColor: colors.bg, justifyContent: 'center', padding: space.xl, gap: space.md },
 });