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/src/app/artist/[id].tsx

@@ -0,0 +1,57 @@
+import { unwrap } from '@pipu/core';
+import { useQuery } from '@tanstack/react-query';
+import { useLocalSearchParams, useRouter } from 'expo-router';
+import { useTranslation } from 'react-i18next';
+import { FlatList, Pressable, Text, View } from 'react-native';
+
+import { useSession } from '../../lib/session';
+import { colors } from '../../theme';
+import { Cover, Icon, Screen } from '../../ui/kit';
+
+export default function ArtistScreen() {
+  const { id } = useLocalSearchParams<{ id: string }>();
+  const { t } = useTranslation();
+  const router = useRouter();
+  const session = useSession();
+  const artist = useQuery({
+    queryKey: ['artist', id],
+    queryFn: async () => unwrap(await session.client.GET('/api/v1/artists/{id}', { params: { path: { id } } })),
+  });
+  const albums = useQuery({
+    queryKey: ['artist-albums', id],
+    queryFn: async () => unwrap(await session.client.GET('/api/v1/artists/{id}/albums', { params: { path: { id } } })).items,
+  });
+
+  return (
+    <Screen>
+      <FlatList
+        data={albums.data ?? []}
+        keyExtractor={(a) => a.id}
+        numColumns={2}
+        columnWrapperStyle={{ gap: 12, paddingHorizontal: 16 }}
+        contentContainerStyle={{ gap: 16, paddingBottom: 24 }}
+        ListHeaderComponent={
+          <View style={{ padding: 16, gap: 10, alignItems: 'center' }}>
+            <Pressable onPress={() => router.back()} style={{ alignSelf: 'flex-start' }} accessibilityRole="button" accessibilityLabel={t('form.close')}>
+              <Icon name="arrow-back" color={colors.text} />
+            </Pressable>
+            <Cover album={{ id }} size={140} round />
+            <Text style={{ color: colors.text, fontSize: 24, fontWeight: '700' }}>{artist.data?.name ?? '…'}</Text>
+            {artist.data && (
+              <Text style={{ color: colors.text2 }}>
+                {t('catalog.album_count', { count: artist.data.album_count })} · {t('catalog.track_count', { count: artist.data.track_count })}
+              </Text>
+            )}
+          </View>
+        }
+        renderItem={({ item }) => (
+          <Pressable onPress={() => router.push(`/album/${item.id}`)} style={{ flex: 1, gap: 6 }} accessibilityRole="button">
+            <Cover album={item} size={160} />
+            <Text numberOfLines={1} style={{ color: colors.text, fontWeight: '600' }}>{item.title}</Text>
+            <Text style={{ color: colors.text3, fontSize: 12 }}>{item.year ?? ''}</Text>
+          </Pressable>
+        )}
+      />
+    </Screen>
+  );
+}