refactor: voice_*-Prefs hinter VoicePrefs-Fassade in settings_prefs (M2 storage-Leitplanke, gleiche Keys/Semantik)

lib/core/settings_prefs.dart

@@ -90,6 +90,56 @@ final privacyReadReceiptsProvider =
 final privacyTypingProvider =
     StateNotifierProvider<BoolPref, bool>((ref) => BoolPref('privacy_typing', true));
 
+// ── Voice preferences ────────────────────────────────────────────────────────
+// Geschrieben von der Settings-Voice-Sektion, gelesen von den Call-Modulen
+// (call_signaling, voice_channel). Die historischen voice_*-Keys bleiben
+// unverändert, damit bestehende Nutzer-Einstellungen erhalten bleiben.
+
+class VoicePrefs {
+  VoicePrefs._();
+
+  static const _kMic = 'voice_mic_device';
+  static const _kSpeaker = 'voice_speaker_device';
+  static const _kCamera = 'voice_camera_device';
+  static const _kOutputVolume = 'voice_output_volume';
+
+  static Future<double> loadOutputVolume() async {
+    final p = await SharedPreferences.getInstance();
+    return p.getDouble(_kOutputVolume) ?? 1.0;
+  }
+
+  static Future<void> saveOutputVolume(double v) async {
+    final p = await SharedPreferences.getInstance();
+    await p.setDouble(_kOutputVolume, v);
+  }
+
+  /// Gewählte Geräte-IDs; null = kein Pref gesetzt (System-Standard nutzen).
+  static Future<({String? mic, String? speaker, String? camera})>
+      loadDevices() async {
+    final p = await SharedPreferences.getInstance();
+    return (
+      mic: p.getString(_kMic),
+      speaker: p.getString(_kSpeaker),
+      camera: p.getString(_kCamera),
+    );
+  }
+
+  static Future<void> saveMic(String? deviceId) => _saveDevice(_kMic, deviceId);
+  static Future<void> saveSpeaker(String? deviceId) =>
+      _saveDevice(_kSpeaker, deviceId);
+  static Future<void> saveCamera(String? deviceId) =>
+      _saveDevice(_kCamera, deviceId);
+
+  static Future<void> _saveDevice(String key, String? deviceId) async {
+    final p = await SharedPreferences.getInstance();
+    if (deviceId == null || deviceId.isEmpty) {
+      await p.remove(key);
+    } else {
+      await p.setString(key, deviceId);
+    }
+  }
+}
+
 // ── Theme persistence helpers ────────────────────────────────────────────────
 
 Future<void> saveThemePrefs({