refactor(member-card): 更新扩展ID常量值

- 将EXTENSION_ID常量值从'six-shop-member-card'更改为'member_card'

src/Extension.php

@@ -7,7 +7,7 @@ use SixShop\Core\ExtensionAbstract;
 
 class Extension extends ExtensionAbstract
 {
-    public const string EXTENSION_ID = 'six-shop-member-card';
+    public const string EXTENSION_ID = 'member_card';
 
     protected function getBaseDir(): string
     {