feat(task-0006): implement menu restart button and signal coordination

- Update MenuUIViewModel with IMenuRestartSignal dependency and Restart() method
- Add RestartButton to MenuUIView with listener management in Initialize/Release
- Connect MenuUIView click handler to ViewModel.Restart() callback
- Fix race condition in MenuRestartSignal.RequestRestart() by nulling completion source first
- Wrap MenuState.WaitAsync() in try-catch for proper view cleanup on cancellation
- Update TASK-0006 status to Ready

Выполнена задача TASK-0006: реализована кнопка Restart и координация сигналов

- Обновлён MenuUIViewModel с зависимостью IMenuRestartSignal и методом Restart()
- Добавлена кнопка RestartButton в MenuUIView с управлением слушателями в Initialize/Release
- Подключен обработчик кликов MenuUIView к колбэку ViewModel.Restart()
- Исправлено состояние гонки в MenuRestartSignal.RequestRestart() путем обнуления completion source
- Обёрнут WaitAsync в MenuState в try-catch для корректной очистки view при отмене
- Обновлён статус TASK-0006 до Ready

Assets/Scripts/Boot/Flow/MenuRestartSignal.cs

@@ -17,7 +17,9 @@ namespace QuizPleaseTest.Boot.Flow
 
         public void RequestRestart()
         {
-            _restartCompletionSource?.TrySetResult();
+            UniTaskCompletionSource restartCompletionSource = _restartCompletionSource;
+            _restartCompletionSource = null;
+            restartCompletionSource?.TrySetResult();
         }
     }
 }

Assets/Scripts/Boot/States/MenuState.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Threading;
 using Cysharp.Threading.Tasks;
 using QuizPleaseTest.Boot.Flow;
@@ -19,9 +20,18 @@ namespace QuizPleaseTest.Boot.States
 
         public async UniTask EnterAsync(CancellationToken ct)
         {
-            _view.Bind(new MenuUIViewModel());
+            _view.Bind(new MenuUIViewModel(_restartSignal));
             _view.Initialize();
-            await _restartSignal.WaitAsync(ct);
+
+            try
+            {
+                await _restartSignal.WaitAsync(ct);
+            }
+            catch (OperationCanceledException) when (ct.IsCancellationRequested)
+            {
+                _view.Release();
+                throw;
+            }
         }
 
         public UniTask ExitAsync(CancellationToken ct)

Assets/Scripts/Boot/UI/MenuUIView.cs

@@ -1,8 +1,39 @@
 using QuizPleaseTest.Common.UI;
+using UnityEngine;
+using UnityEngine.UI;
 
 namespace QuizPleaseTest.Boot.UI
 {
     public class MenuUIView : UIView<MenuUIViewModel>
     {
+        [field: SerializeField] public Button RestartButton { get; private set; }
+
+        public override void Initialize()
+        {
+            base.Initialize();
+
+            if (RestartButton == null)
+            {
+                return;
+            }
+
+            RestartButton.onClick.RemoveListener(OnRestartClicked);
+            RestartButton.onClick.AddListener(OnRestartClicked);
+        }
+
+        public override void Release()
+        {
+            if (RestartButton != null)
+            {
+                RestartButton.onClick.RemoveListener(OnRestartClicked);
+            }
+
+            base.Release();
+        }
+
+        private void OnRestartClicked()
+        {
+            ViewModel.Restart();
+        }
     }
 }

Assets/Scripts/Boot/UI/MenuUIViewModel.cs

@@ -1,8 +1,21 @@
+using System;
+using QuizPleaseTest.Boot.Flow;
 using QuizPleaseTest.Common.UI;
 
 namespace QuizPleaseTest.Boot.UI
 {
     public class MenuUIViewModel : IUIViewModel
     {
+        private readonly IMenuRestartSignal _restartSignal;
+
+        public MenuUIViewModel(IMenuRestartSignal restartSignal)
+        {
+            _restartSignal = restartSignal ?? throw new ArgumentNullException(nameof(restartSignal));
+        }
+
+        public void Restart()
+        {
+            _restartSignal.RequestRestart();
+        }
     }
 }