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/login.tsx

@@ -0,0 +1,51 @@
+import { useState } from 'react';
+import { useTranslation } from 'react-i18next';
+import { ScrollView } from 'react-native';
+
+import { useSessionCtx } from '../lib/session';
+import { Button, ErrorBox, Field, H1, Muted, Screen, useErrorText } from '../ui/kit';
+
+export default function LoginScreen() {
+  const { t } = useTranslation(['auth', 'common']);
+  const { server, session, disconnect } = useSessionCtx();
+  const errorText = useErrorText();
+  const [username, setUsername] = useState('');
+  const [password, setPassword] = useState('');
+  const [busy, setBusy] = useState(false);
+  const [error, setError] = useState<unknown>(null);
+
+  const submit = async () => {
+    if (!session) return;
+    setBusy(true);
+    setError(null);
+    try {
+      await session.login(username.trim(), password); // переход сделает Gate
+    } catch (e) {
+      setError(e);
+      setPassword('');
+    } finally {
+      setBusy(false);
+    }
+  };
+
+  return (
+    <Screen>
+      <ScrollView contentContainerStyle={{ padding: 20, gap: 14, flexGrow: 1, justifyContent: 'center' }} keyboardShouldPersistTaps="handled">
+        <H1>{t('login.title')}</H1>
+        <Muted>{server?.replace(/^https?:\/\//, '')}</Muted>
+        <Field label={t('login.username')} value={username} onChangeText={setUsername} autoComplete="username" />
+        <Field
+          label={t('login.password')}
+          value={password}
+          onChangeText={setPassword}
+          secure
+          autoComplete="password"
+          onSubmitEditing={() => void submit()}
+        />
+        <ErrorBox>{error ? errorText(error) : null}</ErrorBox>
+        <Button title={t('login.submit')} onPress={() => void submit()} busy={busy} disabled={!username.trim() || !password} />
+        <Button title={t('common:mobile.change_server')} variant="ghost" onPress={() => void disconnect()} />
+      </ScrollView>
+    </Screen>
+  );
+}