fix(ios-audio): add voice join session coordinator

apps/chanora_flutter/lib/services/voice_join_ordering.dart

@@ -0,0 +1,23 @@
+typedef VoiceJoinCallback = Future<void> Function({
+  required BigInt channelId,
+  required String password,
+});
+
+typedef IosVoiceSessionActivation = Future<void> Function();
+typedef IosVoiceSessionDeactivation = Future<void> Function();
+
+Future<void> joinVoiceChannelWithIosAudioSession({
+  required BigInt channelId,
+  required String password,
+  required VoiceJoinCallback voiceJoin,
+  required IosVoiceSessionActivation activateIosAudioSession,
+  required IosVoiceSessionDeactivation deactivateIosAudioSession,
+}) async {
+  await activateIosAudioSession();
+  try {
+    await voiceJoin(channelId: channelId, password: password);
+  } catch (_) {
+    await deactivateIosAudioSession();
+    rethrow;
+  }
+}

apps/chanora_flutter/test/services/voice_join_ordering_test.dart

@@ -0,0 +1,58 @@
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:chanora_flutter/services/voice_join_ordering.dart';
+
+void main() {
+  group('joinVoiceChannelWithIosAudioSession', () {
+    test('activates the iOS audio session before Rust voiceJoin', () async {
+      final calls = <String>[];
+
+      await joinVoiceChannelWithIosAudioSession(
+        channelId: BigInt.from(42),
+        password: 'secret',
+        activateIosAudioSession: () async {
+          calls.add('activateIosAudioSession');
+        },
+        deactivateIosAudioSession: () async {
+          calls.add('deactivateIosAudioSession');
+        },
+        voiceJoin: ({required channelId, required password}) async {
+          expect(channelId, BigInt.from(42));
+          expect(password, 'secret');
+          calls.add('voiceJoin');
+        },
+      );
+
+      expect(calls, ['activateIosAudioSession', 'voiceJoin']);
+    });
+
+    test('deactivates the iOS audio session when Rust voiceJoin fails',
+        () async {
+      final calls = <String>[];
+
+      await expectLater(
+        joinVoiceChannelWithIosAudioSession(
+          channelId: BigInt.from(42),
+          password: '',
+          activateIosAudioSession: () async {
+            calls.add('activateIosAudioSession');
+          },
+          deactivateIosAudioSession: () async {
+            calls.add('deactivateIosAudioSession');
+          },
+          voiceJoin: ({required channelId, required password}) async {
+            calls.add('voiceJoin');
+            throw StateError('join rejected');
+          },
+        ),
+        throwsStateError,
+      );
+
+      expect(calls, [
+        'activateIosAudioSession',
+        'voiceJoin',
+        'deactivateIosAudioSession',
+      ]);
+    });
+  });
+}