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/UI/UIItems/RoleItem.prefab

@@ -210,6 +210,39 @@ MonoBehaviour:
   m_Script: {fileID: 11500000, guid: a5079836f95c2a44b96fa331487ebb70, type: 3}
   m_Name: 
   m_EditorClassIdentifier: 
+  m_Navigation:
+    m_Mode: 3
+    m_WrapAround: 0
+    m_SelectOnUp: {fileID: 0}
+    m_SelectOnDown: {fileID: 0}
+    m_SelectOnLeft: {fileID: 0}
+    m_SelectOnRight: {fileID: 0}
+  m_Transition: 0
+  m_Colors:
+    m_NormalColor: {r: 1, g: 1, b: 1, a: 1}
+    m_HighlightedColor: {r: 0.9607843, g: 0.9607843, b: 0.9607843, a: 1}
+    m_PressedColor: {r: 0.78431374, g: 0.78431374, b: 0.78431374, a: 1}
+    m_SelectedColor: {r: 0.9607843, g: 0.9607843, b: 0.9607843, a: 1}
+    m_DisabledColor: {r: 0.78431374, g: 0.78431374, b: 0.78431374, a: 0.5019608}
+    m_ColorMultiplier: 1
+    m_FadeDuration: 0.1
+  m_SpriteState:
+    m_HighlightedSprite: {fileID: 0}
+    m_PressedSprite: {fileID: 0}
+    m_SelectedSprite: {fileID: 0}
+    m_DisabledSprite: {fileID: 0}
+  m_AnimationTriggers:
+    m_NormalTrigger: Normal
+    m_HighlightedTrigger: Highlighted
+    m_PressedTrigger: Pressed
+    m_SelectedTrigger: Selected
+    m_DisabledTrigger: Disabled
+  m_Interactable: 1
+  m_TargetGraphic: {fileID: 0}
+  m_OnClick:
+    m_PersistentCalls:
+      m_Calls: []
+  _background: {fileID: 7726133595027118117}
   _onPointerEnterAction:
     m_PersistentCalls:
       m_Calls:
@@ -255,5 +288,4 @@ MonoBehaviour:
   m_Script: {fileID: 11500000, guid: 35de2974f065de547952f8d5cbb9f6fe, type: 3}
   m_Name: 
   m_EditorClassIdentifier: 
-  _button: {fileID: 3813327180119752992}
   _roleImage: {fileID: 6878033219184294131}