feat(task-0002): implement state controller interface with cancellation support and update task status

- Refactor BootStatesController to implement IStatesController interface
- Move state dictionary creation into constructor, remove static helper method
- Add CancellationToken validation before state transitions in StatesController
- Track current state presence with _hasCurrentState flag for safety
- Update TASK-0002 with Ready status

Выполнена задача TASK-0002 и обновлён статус:
- Рефакторинг BootStatesController для реализации интерфейса IStatesController
- Перемещено создание словаря состояний в конструктор, удалён статический вспомогательный метод
- Добавлена валидация CancellationToken перед переходами между состояниями в StatesController
- Добавлен флаг _hasCurrentState для отслеживания текущего состояния
- Обновлён статус TASK-0002 до Ready

Assets/Scripts/Boot/States/BootStatesController.cs

@@ -1,29 +1,31 @@
 using System.Collections.Generic;
+using System.Threading;
+using Cysharp.Threading.Tasks;
 using QuizPleaseTest.Common.StateMachine;
 
 namespace QuizPleaseTest.Boot.States
 {
-    public class BootStatesController : StatesController<BootStateCode>
+    public class BootStatesController : IStatesController<BootStateCode>
     {
+        private readonly StatesController<BootStateCode> _statesController;
+
         public BootStatesController(
             SplashState splashState,
             LoadState loadState,
             MenuState menuState)
-            : base(CreateStates(splashState, loadState, menuState))
         {
+            _statesController = new StatesController<BootStateCode>(
+                new Dictionary<BootStateCode, IState>
+                {
+                    { BootStateCode.Splash, splashState },
+                    { BootStateCode.Load, loadState },
+                    { BootStateCode.Menu, menuState }
+                });
         }
 
-        private static IReadOnlyDictionary<BootStateCode, IState> CreateStates(
-            SplashState splashState,
-            LoadState loadState,
-            MenuState menuState)
+        public UniTask EnterStateAsync(BootStateCode code, CancellationToken ct)
         {
-            return new Dictionary<BootStateCode, IState>
-            {
-                { BootStateCode.Splash, splashState },
-                { BootStateCode.Load, loadState },
-                { BootStateCode.Menu, menuState }
-            };
+            return _statesController.EnterStateAsync(code, ct);
         }
     }
 }