refactor(limit-purchase): 更新扩展ID命名规范

- 将扩展ID从连字符格式改为下划线格式
- 统一composer.json中的扩展标识符命名
- 确保与系统其他模块命名一致性

composer.json

@@ -25,7 +25,7 @@
   },
   "extra": {
     "sixshop": {
-      "id": "limit-purchase",
+      "id": "limit_purchase",
       "class": "SixShop\\LimitPurchase\\Extension"
     }
   }

src/Extension.php

@@ -7,7 +7,7 @@ use SixShop\Core\ExtensionAbstract;
 
 class Extension extends ExtensionAbstract
 {
-    public const string EXTENSION_ID = 'limit-purchase';
+    public const string EXTENSION_ID = 'limit_purchase';
 
     #[\Override]
     public function getHooks(): array