feat(task-0005): implement splash delay and loading progress with reactive properties

- Add SplashState delay timer using BootSettings.SplashDurationSeconds with cancellation support
- Implement LoadState progress tracking via ReactiveProperty<float> with step-by-step updates
- Update LoadingUIViewModel to accept and expose Progress reactive property
- Connect LoadingUIView to ViewModel progress changes using UniRx subscriptions
- Add CompositeDisposable for proper cleanup of UI subscriptions in Release()
- Scale ProgressFill transform based on progress value for visual feedback

Выполнена задача TASK-0005 и реализованы splash и loading состояния:
- Добавлен таймер задержки в SplashState с использованием BootSettings.SplashDurationSeconds и поддержкой отмены
- Реализован трекинг прогресса в LoadState через ReactiveProperty<float> со пошаговыми обновлениями
- Обновлён LoadingUIViewModel для принятия и экспорта реактивного свойства Progress
- Подключён LoadingUIView к изменениям прогресса ViewModel с использованием подписок UniRx
- Добавлен CompositeDisposable для правильной очистки UI подписок в Release()
- Масштабирование ProgressFill на основе значения прогресса для визуальной обратной связи

Assets/Scripts/Boot/States/LoadState.cs

@@ -1,24 +1,49 @@
+using System;
 using System.Threading;
 using Cysharp.Threading.Tasks;
+using QuizPleaseTest.Boot.Settings;
 using QuizPleaseTest.Boot.UI;
 using QuizPleaseTest.Common.StateMachine;
+using UniRx;
 
 namespace QuizPleaseTest.Boot.States
 {
     public class LoadState : IState
     {
         private readonly LoadingUIView _view;
+        private readonly BootSettings _settings;
+        private readonly ReactiveProperty<float> _progress = new ReactiveProperty<float>(0f);
 
-        public LoadState(LoadingUIView view)
+        public IReadOnlyReactiveProperty<float> Progress => _progress;
+
+        public LoadState(LoadingUIView view, BootSettings settings)
         {
             _view = view;
+            _settings = settings;
         }
 
-        public UniTask EnterAsync(CancellationToken ct)
+        public async UniTask EnterAsync(CancellationToken ct)
         {
-            _view.Bind(new LoadingUIViewModel());
+            _progress.Value = 0f;
+            _view.Bind(new LoadingUIViewModel(Progress));
             _view.Initialize();
-            return UniTask.CompletedTask;
+
+            int loadSteps = _settings.LoadSteps > 0 ? _settings.LoadSteps : 1;
+            int stepDurationMs = _settings.LoadStepDurationMs > 0 ? _settings.LoadStepDurationMs : 0;
+
+            try
+            {
+                for (int step = 1; step <= loadSteps; step++)
+                {
+                    await UniTask.Delay(stepDurationMs, cancellationToken: ct);
+                    _progress.Value = (float)step / loadSteps;
+                }
+            }
+            catch (OperationCanceledException) when (ct.IsCancellationRequested)
+            {
+                _view.Release();
+                throw;
+            }
         }
 
         public UniTask ExitAsync(CancellationToken ct)