fix: 6 Claude-Audit-Fixes (3 CRIT + 3 HIGH)

CRITICAL:
- Logout: LoginScreen statt MeloHome pushen (home_screen.dart)
- Path Traversal: sanitizeDateiname() zentral + sync-loop abgesichert
- SecureStorage: flutter_secure_storage für Token+Passwort (auth_service, navidrome)

HIGH:
- Seek: PlayerService.seek() reload-frei (audio_handler)
- Play/Pause: Zielzustand statt Toggle für System-Controls
- X-User: Header entfernt, Server verlässt sich auf JWT

lib/screens/cloud_screen.dart

@@ -5,6 +5,7 @@ import 'package:path_provider/path_provider.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:flutter_local_notifications/flutter_local_notifications.dart';
 import '../utils/farb_theme.dart';
+import '../utils/sanitize.dart';
 import '../services/cloud_service.dart';
 import '../services/auth_service.dart';
 import '../database/db_helper.dart';
@@ -216,7 +217,8 @@ class _CloudScreenState extends State<CloudScreen> {
 
         _updateSync('Download: $title...',
             0.1 + (0.4 * processed / (totalNew > 0 ? totalNew : 1)));
-        final dest = '${dir.path}/$title';
+        final safeTitle = sanitizeDateiname(title);
+        final dest = '${dir.path}/$safeTitle';
         if (await widget.cloud.download(sid, dest)) {
           downloaded++;
           // In DB eintragen mit cloud_id

lib/screens/home_screen.dart

@@ -12,6 +12,7 @@ import '../widgets/song_tile.dart';
 import 'download_screen.dart';
 import 'cloud_screen.dart';
 import 'settings_screen.dart';
+import 'login_screen.dart';
 import '../services/cloud_service.dart';
 import '../services/auth_service.dart';
 import '../config/app_config.dart';
@@ -397,7 +398,7 @@ class _MeloHomeState extends State<MeloHome> {
         await AuthService().logout();
         if (mounted) {
           Navigator.of(context).pushReplacement(
-            MaterialPageRoute(builder: (_) => const MeloHome()),
+            MaterialPageRoute(builder: (_) => const LoginScreen()),
           );
         }
         break;

lib/services/audio_handler.dart

@@ -54,20 +54,20 @@ class MeloAudioHandler extends BaseAudioHandler {
   Future<void> play() async {
     if (_player.aktuellerSong != null) {
       _playing = true;
-      await _player.playPause();
+      await _player.play();
     }
   }
 
   @override
   Future<void> pause() async {
     _playing = false;
-    await _player.playPause();
+    await _player.pause();
   }
 
   @override
   Future<void> stop() async {
     _playing = false;
-    await _player.playPause();
+    await _player.pause();
     playbackState.add(playbackState.value.copyWith(
       controls: [MediaControl.play],
       playing: false,
@@ -77,7 +77,7 @@ class MeloAudioHandler extends BaseAudioHandler {
 
   @override
   Future<void> seek(Duration position) async {
-    _player.spiele(_player.aktuellerSong!, position: position.inSeconds);
+    await _player.seek(position);
   }
 
   @override

lib/services/auth_service.dart

@@ -1,6 +1,6 @@
 import 'dart:convert';
 import 'package:http/http.dart' as http;
-import 'package:shared_preferences/shared_preferences.dart';
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
 import '../config/app_config.dart';
 import '../services/melo_logger.dart';
 
@@ -11,6 +11,8 @@ class AuthService {
   factory AuthService() => _instance;
   AuthService._();
 
+  final FlutterSecureStorage _secure = const FlutterSecureStorage();
+
   String? _token;
   String _user = '';
   bool _initialisiert = false;
@@ -34,9 +36,8 @@ class AuthService {
   Future<bool> initialisieren() async {
     if (_initialisiert) return istEingeloggt;
     try {
-      final prefs = await SharedPreferences.getInstance();
-      _token = prefs.getString('baka_token');
-      _user = prefs.getString('baka_user') ?? '';
+      _token = await _secure.read(key: 'baka_token');
+      _user = await _secure.read(key: 'baka_user') ?? '';
 
       if (_token != null && _token!.isNotEmpty) {
         // Token beim Server validieren (nicht blind vertrauen)
@@ -46,8 +47,8 @@ class AuthService {
           MeloLogger().zustand('auth_token_expired', {'user': _user});
           _token = null;
           _user = '';
-          await prefs.remove('baka_token');
-          await prefs.remove('baka_user');
+          await _secure.delete(key: 'baka_token');
+          await _secure.delete(key: 'baka_user');
         } else {
           MeloLogger().zustand('auth_restored', {'user': _user});
         }
@@ -100,9 +101,8 @@ class AuthService {
         _user = user;
 
         if (_token != null && _token!.isNotEmpty) {
-          final prefs = await SharedPreferences.getInstance();
-          await prefs.setString('baka_token', _token!);
-          await prefs.setString('baka_user', _user);
+          await _secure.write(key: 'baka_token', value: _token!);
+          await _secure.write(key: 'baka_user', value: _user);
           MeloLogger().aktion('auth_login_ok', {'user': _user});
           return AuthResult.ok;
         }
@@ -144,9 +144,8 @@ class AuthService {
         _user = user;
 
         if (_token != null && _token!.isNotEmpty) {
-          final prefs = await SharedPreferences.getInstance();
-          await prefs.setString('baka_token', _token!);
-          await prefs.setString('baka_user', _user);
+          await _secure.write(key: 'baka_token', value: _token!);
+          await _secure.write(key: 'baka_user', value: _user);
           MeloLogger().aktion('auth_register_ok', {'user': _user});
           return AuthResult.ok;
         }
@@ -172,9 +171,8 @@ class AuthService {
   Future<void> logout() async {
     _token = null;
     _user = '';
-    final prefs = await SharedPreferences.getInstance();
-    await prefs.remove('baka_token');
-    await prefs.remove('baka_user');
+    await _secure.delete(key: 'baka_token');
+    await _secure.delete(key: 'baka_user');
     MeloLogger().aktion('auth_logout', {});
   }
 }

lib/services/cloud_service.dart

@@ -11,11 +11,9 @@ class CloudService {
   static final http.Client _client = http.Client();
 
   static String get _base => AppConfig.cloudUrl;
-  String _user = '';
 
   /// Login mit Baka-Auth – Token wird aus AuthService bezogen
   Future<bool> login(String user) async {
-    _user = user;
     try {
       final r = await _client
           .get(Uri.parse('$_base/api/cloud/status'),
@@ -32,9 +30,6 @@ class CloudService {
     final headers = <String, String>{
       'X-API-Key': AppConfig.ytProxyApiKey,
     };
-    if (_user.isNotEmpty) {
-      headers['X-User'] = _user;
-    }
     if (token != null && token.isNotEmpty) {
       headers['Authorization'] = 'Bearer $token';
     }

lib/services/download_service.dart

@@ -12,6 +12,7 @@ import '../utils/audio_validator.dart';
 import 'melo_logger.dart';
 import '../config/app_config.dart';
 import '../main.dart'; // für notificationsPlugin
+import '../utils/sanitize.dart';
 
 /// Download-Service: Lädt YouTube-Audio über den yt-proxy herunter.
 /// Nutzt ChangeNotifier für UI-Updates via ListenableBuilder.
@@ -292,9 +293,9 @@ class DownloadService extends ChangeNotifier {
           : Directory('${(await getApplicationDocumentsDirectory()).path}/music');
       if (!await dir.exists()) await dir.create(recursive: true);
 
-      // Sicheren Dateinamen erstellen
-      final safeName = titel.replaceAll(RegExp(r'[^\w\s-]'), '').trim();
-      final lokalerName = '${safeName.isEmpty ? "song" : safeName}.mp3';
+      // Sicheren Dateinamen erstellen (zentrale Sanitize-Funktion)
+      final safeName = sanitizeDateiname(titel);
+      final lokalerName = '$safeName.mp3';
       dateiPfad = '${dir.path}/$lokalerName';
 
       final stopwatch2 = Stopwatch()..start();

lib/services/navidrome_service.dart

@@ -5,8 +5,10 @@ import 'package:crypto/crypto.dart';
 import 'package:http/http.dart' as http;
 import 'package:path_provider/path_provider.dart';
 import 'package:shared_preferences/shared_preferences.dart';
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
 import '../models/song.dart';
 import '../database/db_helper.dart';
+import '../utils/sanitize.dart';
 
 /// Ein Song aus der Subsonic-API
 class SubsonicSong {
@@ -63,6 +65,7 @@ class SubsonicAlbum {
 
 class NavidromeService {
   final DbHelper _db = DbHelper();
+  final FlutterSecureStorage _secure = const FlutterSecureStorage();
 
   String _serverUrl = '';
   String _user = '';
@@ -86,7 +89,7 @@ class NavidromeService {
       final prefs = await SharedPreferences.getInstance();
       final url = prefs.getString('navidrome_url');
       final user = prefs.getString('navidrome_user');
-      final pass = prefs.getString('navidrome_pass');
+      final pass = await _secure.read(key: 'navidrome_pass');
       if (url != null && user != null && pass != null && url.isNotEmpty) {
         setCredentials(url, user, pass);
       }
@@ -101,7 +104,7 @@ class NavidromeService {
       final prefs = await SharedPreferences.getInstance();
       await prefs.setString('navidrome_url', url);
       await prefs.setString('navidrome_user', user);
-      await prefs.setString('navidrome_pass', password);
+      await _secure.write(key: 'navidrome_pass', value: password);
     } catch (e) {
       debugPrint('Fehler beim Speichern der Navidrome-Zugangsdaten: $e');
     }
@@ -178,9 +181,9 @@ class NavidromeService {
       final musikDir = Directory('${dir.path}/music');
       if (!await musikDir.exists()) await musikDir.create(recursive: true);
 
-      final safeName = s.titel.replaceAll(RegExp(r'[^\w\s-]'), '').trim();
+      final safeName = sanitizeDateiname(s.titel);
       final kurzId = s.id.length > 8 ? s.id.substring(0, 8) : s.id;
-      final dateiName = '${safeName.isEmpty ? "song" : safeName}_$kurzId.mp3';
+      final dateiName = '${safeName}_$kurzId.mp3';
       final dateiPfad = '${musikDir.path}/$dateiName';
 
       final file = File(dateiPfad);

lib/services/player_service.dart

@@ -86,6 +86,24 @@ class PlayerService {
     }
   }
 
+  /// Explizit abspielen (kein Toggle) — für System-Controls (Bluetooth, etc.)
+  Future<void> play() async {
+    if (_player == null || aktuellerSong == null) return;
+    await _p.play();
+  }
+
+  /// Explizit pausieren (kein Toggle) — für System-Controls (Bluetooth, etc.)
+  Future<void> pause() async {
+    if (_player == null) return;
+    await _p.pause();
+  }
+
+  /// Nur seeken ohne Reload der Quelle
+  Future<void> seek(Duration position) async {
+    if (_player == null) return;
+    await _p.seek(position);
+  }
+
   Future<void> vorheriges() async {
     if (_player == null || aktuellerSong == null) return;
     final pos = _p.position;

lib/utils/sanitize.dart

@@ -0,0 +1,24 @@
+/// Zentrale Sanitize-Funktion für Dateinamen.
+/// Verhindert Path-Traversal (../), Null-Bytes und andere gefährliche Zeichen.
+String sanitizeDateiname(String name) {
+  // 1. Extrahiere nur den Dateinamen (keine Pfad-Komponenten)
+  var safe = name.split('/').last.split('\\').last;
+
+  // 2. Entferne NULL-Bytes und andere gefährliche Steuerzeichen
+  safe = safe.replaceAll(RegExp(r'[\x00-\x1F\x7F]'), '');
+
+  // 3. Entferne alles außer Wort-Zeichen, Leerzeichen und Bindestrichen
+  safe = safe.replaceAll(RegExp(r'[^\w\s.-]'), '');
+
+  // 4. Entferne führende Punkte (versteckte Dateien)
+  safe = safe.replaceAll(RegExp(r'^\.+'), '');
+
+  // 5. Trimmen und Default-Name falls leer
+  safe = safe.trim();
+  if (safe.isEmpty) safe = 'unknown';
+
+  // 6. Auf sinnvolle Länge kürzen (255 Zeichen ist typisches Dateisystem-Limit)
+  if (safe.length > 200) safe = safe.substring(0, 200);
+
+  return safe;
+}

lib/viewmodels/melo_home_viewmodel.dart

@@ -269,7 +269,7 @@ class MeloHomeViewModel extends ChangeNotifier {
   @override
   void dispose() {
     _positionsSub?.cancel();
-    player.dispose();
+    // PlayerService ist Singleton — nicht hier disposesen, lebt für die App-Lebensdauer
     super.dispose();
   }
 }