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/(tabs)/index.tsx

@@ -3,13 +3,15 @@ import { useEffect, useState } from 'react';
 import { FlatList, RefreshControl, StyleSheet, Text, View } from 'react-native';
 import { SafeAreaView } from 'react-native-safe-area-context';
 import useSWR from 'swr';
-import { sortFeed, type FeedItemDTO, type ProfileDTO } from '@musicshare/shared';
+import { sortFeed, type ConnectionDTO, type FeedItemDTO, type ProfileDTO } from '@musicshare/shared';
 import { NowPlayingCard } from '@/components/NowPlayingCard';
 import { SharingControls } from '@/components/SharingControls';
 import { Body, Button, Card, Title } from '@/components/ui';
 import { api } from '@/lib/api';
 import { showError } from '@/lib/errors';
-import { shouldOfferSetup, useReader } from '@/lib/nowPlayingReader';
+import { appleMusicAvailable } from '@/lib/appleMusic';
+import { useReader } from '@/lib/nowPlayingReader';
+import { shouldOfferSetup } from '@/lib/setup';
 import { useRealtime } from '@/lib/useRealtime';
 import { useSession } from '@/lib/session';
 import { colors, space } from '@/lib/theme';
@@ -22,6 +24,8 @@ export default function FeedScreen() {
   const [refreshing, setRefreshing] = useState(false);
 
   const reader = useReader();
+  const { data: connections } = useSWR<ConnectionDTO[]>(appleMusicAvailable ? '/connections' : null);
+  const offerAppleMusic = appleMusicAvailable && connections !== undefined && connections.length === 0;
 
   // First run on Android: open the one-tap setup once (deferred so navigation has mounted).
   useEffect(() => {
@@ -74,6 +78,12 @@ export default function FeedScreen() {
         ListHeaderComponent={
           <View style={styles.header}>
             <SharingControls compact />
+            {offerAppleMusic && (
+              <Card>
+                <Body>Connect Apple Music so friends see what you play. One tap.</Body>
+                <Button small variant="primary" title="Connect" onPress={() => router.push('/share-setup')} style={{ alignSelf: 'flex-start' }} />
+              </Card>
+            )}
             {reader.available && !reader.granted && (
               <Card>
                 <Body>Share what you’re playing in Spotify, YouTube Music and other apps. One tap, no accounts.</Body>