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

lib/features/call_signaling/voip_manager.dart

@@ -3,9 +3,9 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_webrtc/flutter_webrtc.dart' as rtc;
 import 'package:matrix/matrix.dart';
-import 'package:shared_preferences/shared_preferences.dart';
 import 'package:webrtc_interface/webrtc_interface.dart';
 import 'package:pyramid/core/ice_servers.dart';
+import 'package:pyramid/core/settings_prefs.dart';
 import 'package:pyramid/features/call_signaling/call_signaling_service.dart';
 import 'package:pyramid/widgets/screen_share_picker.dart';
 
@@ -272,8 +272,7 @@ class PyramidVoipManager extends CallSignalingService
     var v = value;
     if (v == null) {
       try {
-        final prefs = await SharedPreferences.getInstance();
-        v = prefs.getDouble('voice_output_volume') ?? 1.0;
+        v = await VoicePrefs.loadOutputVolume();
       } catch (_) {
         v = 1.0;
       }
@@ -467,10 +466,10 @@ class MediaDevicesWrapper extends MediaDevices {
     // In den Einstellungen gewählte Geräte (voice_*_device Prefs) anwenden —
     // nur wenn kein Screenshare-Source gesetzt ist (sonst nicht anfassen).
     try {
-      final prefs = await SharedPreferences.getInstance();
-      final mic = prefs.getString('voice_mic_device');
-      final cam = prefs.getString('voice_camera_device');
-      final speaker = prefs.getString('voice_speaker_device');
+      final devicePrefs = await VoicePrefs.loadDevices();
+      final mic = devicePrefs.mic;
+      final cam = devicePrefs.camera;
+      final speaker = devicePrefs.speaker;
       if (mic != null &&
           improvedConstraints['audio'] != null &&
           improvedConstraints['audio'] != false) {