接入菜单导航并改造通用按钮交互

- 将 CommonButton 改为基于 Unity Button 实现，保留原有 pointer enter、click、pointer exit 三类事件配置，同时接入 Selectable/Button 的导航、选中和提交能力。补充 CommonButton 自定义 Inspector，保留项目自定义事件与背景配置的编辑体验。

- 同步调整菜单相关 UI，将 StartMenuForm 迁移为 MenuForm，并更新 UIForm 配置、菜单 Controller/Form 以及相关 prefab 引用。更新多个 UI prefab 和通用按钮 prefab，使菜单、商店、角色选择、道具展示等界面能够使用新的按钮选中与导航交互。

Assets/GameMain/Scripts/Presentation/Menu/Menu/MenuController.cs

@@ -53,7 +53,7 @@ namespace SepCore.UI
 
         public override void BindUseCase(IUIUseCase useCase)
         {
-            Log.Info("StartMenuForm doesn't need UseCase");
+            Log.Info("MenuForm doesn't need UseCase");
         }
 
         private void OnMenuStartGameButtonClick(object sender, GameEventArgs e)

Assets/GameMain/Scripts/Presentation/Menu/Menu/MenuForm.cs

@@ -1,12 +1,20 @@
 using SepCore.Event;
+using UnityEngine;
+using UnityEngine.EventSystems;
 using UnityGameFramework.Runtime;
 
 namespace SepCore.UI
 {
     public class MenuForm : UGuiForm
     {
+        [SerializeField] private GameObject _defaultButton;
+
         public void RefreshUI(MenuContext context)
         {
+            if (EventSystem.current.currentSelectedGameObject != _defaultButton)
+            {
+                EventSystem.current.SetSelectedGameObject(this._defaultButton);
+            }
         }
 
         #region Lifecycle
@@ -21,7 +29,7 @@ namespace SepCore.UI
                 return;
             }
 
-            Log.Warning("StartMenuForm requires StartMenuFormContext as userData.");
+            Log.Warning("MenuForm requires MenuFormContext as userData.");
         }
 
         protected override void OnClose(bool isShutdown, object userData)