feat: 订单来源追踪，保存 src_host / src_url 到订单记录

iframe 嵌入充值页面时 URL 自动附带来源参数，写入数据库用于追踪分析。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/admin/page.tsx

@@ -31,6 +31,8 @@ interface AdminOrderDetail extends AdminOrder {
   failedAt: string | null;
   updatedAt: string;
   clientIp: string | null;
+  srcHost: string | null;
+  srcUrl: string | null;
   paymentSuccess?: boolean;
   rechargeSuccess?: boolean;
   rechargeStatus?: string;