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/UIForms/ShopForm.prefab

@@ -695,7 +695,7 @@ RectTransform:
   m_LocalEulerAnglesHint: {x: 0, y: 0, z: 0}
   m_AnchorMin: {x: 0, y: 1}
   m_AnchorMax: {x: 1, y: 1}
-  m_AnchoredPosition: {x: 2, y: 0.000067918794}
+  m_AnchoredPosition: {x: 2, y: 0.0005856944}
   m_SizeDelta: {x: -2, y: 300}
   m_Pivot: {x: 0, y: 1}
 --- !u!1 &3529895034686484875
@@ -1678,7 +1678,7 @@ MonoBehaviour:
   m_HandleRect: {fileID: 8982130026310361329}
   m_Direction: 2
   m_Value: 0
-  m_Size: 0.99999577
+  m_Size: 0.9549088
   m_NumberOfSteps: 0
   m_OnValueChanged:
     m_PersistentCalls:
@@ -3406,6 +3406,11 @@ PrefabInstance:
       propertyPath: m_LocalEulerAnglesHint.z
       value: 0
       objectReference: {fileID: 0}
+    - target: {fileID: 1939791114573821530, guid: 9f5bba6d2f5c95049a59fcb56df2d38f,
+        type: 3}
+      propertyPath: m_text
+      value: 40 <sprite name="coin" index=0>
+      objectReference: {fileID: 0}
     - target: {fileID: 3072890538777882148, guid: 9f5bba6d2f5c95049a59fcb56df2d38f,
         type: 3}
       propertyPath: m_Name