feat(flutter): persist voice settings and per-user volume (TODO-039,040)

Add SharedPreferences persistence for transmit mode, release tail,
input/output device. Per-user volume/mute persisted across sessions.

apps/chanora_flutter/lib/widgets/audio_device_list_tile.dart

@@ -27,6 +27,7 @@ class AudioDeviceListTile extends StatefulWidget {
     AudioDeviceListLoader? loadDevices,
     AudioDeviceSetter? setInputDevice,
     AudioDeviceSetter? setOutputDevice,
+    this.onDeviceChanged,
   }) : loadDevices = loadDevices ?? rust.listAudioDevices,
        setInputDevice = setInputDevice ?? rust.setInputDevice,
        setOutputDevice = setOutputDevice ?? rust.setOutputDevice;
@@ -46,6 +47,10 @@ class AudioDeviceListTile extends StatefulWidget {
   /// Selects an output device.
   final AudioDeviceSetter setOutputDevice;
 
+  /// Called after a device selection succeeds. Receives the device id
+  /// (null for system default).
+  final ValueChanged<String?>? onDeviceChanged;
+
   @override
   State<AudioDeviceListTile> createState() => _AudioDeviceListTileState();
 }
@@ -88,6 +93,7 @@ class _AudioDeviceListTileState extends State<AudioDeviceListTile> {
     setState(() {
       _selectedDeviceId = deviceId;
     });
+    widget.onDeviceChanged?.call(deviceId);
 
     final selectedName = _selectedDevice?.name ?? 'System default';
     ScaffoldMessenger.of(context).showSnackBar(

apps/chanora_flutter/lib/widgets/snapshot_view.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
+import 'package:shared_preferences/shared_preferences.dart';
 
 import '../l10n/generated/app_localizations.dart';
 import '../services/channel_spacer.dart';
@@ -571,11 +572,40 @@ class _ClientVolumePreference {
 }
 
 class _ClientVolumePreferences extends ChangeNotifier {
-  _ClientVolumePreferences._();
+  _ClientVolumePreferences._() {
+    _load();
+  }
 
   static final instance = _ClientVolumePreferences._();
 
+  static const _prefsKey = 'client_volume_prefs';
+
   final Map<BigInt, _ClientVolumePreference> _byClientId = {};
+  bool _loaded = false;
+
+  Future<void> _load() async {
+    if (_loaded) return;
+    _loaded = true;
+    try {
+      final prefs = await SharedPreferences.getInstance();
+      final raw = prefs.getStringList(_prefsKey) ?? const [];
+      for (final entry in raw) {
+        final parts = entry.split(':');
+        if (parts.length == 3) {
+          final id = BigInt.tryParse(parts[0]);
+          final volume = double.tryParse(parts[1]);
+          final muted = parts[2] == '1';
+          if (id != null && volume != null) {
+            _byClientId[id] = _ClientVolumePreference(
+              volume: volume,
+              muted: muted,
+            );
+          }
+        }
+      }
+      notifyListeners();
+    } catch (_) {}
+  }
 
   _ClientVolumePreference preferenceFor(BigInt clientId) {
     return _byClientId[clientId] ?? const _ClientVolumePreference();
@@ -588,6 +618,17 @@ class _ClientVolumePreferences extends ChangeNotifier {
       _byClientId.remove(clientId);
     }
     notifyListeners();
+    _save();
+  }
+
+  Future<void> _save() async {
+    try {
+      final prefs = await SharedPreferences.getInstance();
+      final raw = _byClientId.entries
+          .map((e) => '${e.key}:${e.value.volume}:${e.value.muted ? 1 : 0}')
+          .toList();
+      await prefs.setStringList(_prefsKey, raw);
+    } catch (_) {}
   }
 }
 

apps/chanora_flutter/lib/widgets/voice_settings.dart

@@ -47,6 +47,8 @@ class VoiceSettingsDialog extends StatefulWidget {
     this.talkPower,
     this.neededTalkPower,
     this.talkPowerGranted,
+    this.onInputDeviceChanged,
+    this.onOutputDeviceChanged,
   });
 
   final rust.BridgeTransmitMode initialMode;
@@ -58,6 +60,8 @@ class VoiceSettingsDialog extends StatefulWidget {
   final int? talkPower;
   final int? neededTalkPower;
   final bool? talkPowerGranted;
+  final ValueChanged<String?>? onInputDeviceChanged;
+  final ValueChanged<String?>? onOutputDeviceChanged;
 
   @override
   State<VoiceSettingsDialog> createState() => _VoiceSettingsDialogState();
@@ -207,13 +211,15 @@ class _VoiceSettingsDialogState extends State<VoiceSettingsDialog> {
               if (!isAndroidHost && !isIosHost) ...[
                 const Divider(height: 24),
                 const VoiceSectionHeader('Audio devices'),
-                const AudioDeviceListTile(
+                AudioDeviceListTile(
                   label: 'Input',
                   kind: AudioDeviceKind.input,
+                  onDeviceChanged: widget.onInputDeviceChanged,
                 ),
-                const AudioDeviceListTile(
+                AudioDeviceListTile(
                   label: 'Output',
                   kind: AudioDeviceKind.output,
+                  onDeviceChanged: widget.onOutputDeviceChanged,
                 ),
                 const SizedBox(height: 8),
               ],