fix(admin-web): 引荐关系树初始加载时自动展开直推下级

问题：改为递归组件后，当前用户的直推下级不再显示

解决：
- 添加 useEffect 监听 referralTree 数据
- 数据加载完成后自动将直推下级放入 expandedNodes
- 这样页面初始加载时就会显示直推下级

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/admin-web/src/app/(dashboard)/users/[id]/page.tsx

@@ -1,6 +1,6 @@
 'use client';
 
-import { useState, useCallback } from 'react';
+import { useState, useCallback, useEffect } from 'react';
 import { useParams, useRouter } from 'next/navigation';
 import Image from 'next/image';
 import Link from 'next/link';
@@ -164,6 +164,16 @@ export default function UserDetailPage() {
   // 获取授权信息
   const { data: authData, isLoading: authLoading } = useAuthorizationDetail(accountSequence);
 
+  // 当 referralTree 数据加载完成后，自动展开当前用户的直推下级
+  useEffect(() => {
+    if (referralTree && referralTree.directReferrals.length > 0) {
+      setExpandedNodes((prev) => ({
+        ...prev,
+        [referralTree.currentUser.accountSequence]: referralTree.directReferrals,
+      }));
+    }
+  }, [referralTree]);
+
   // 切换推荐关系树的根节点
   const handleTreeNodeClick = useCallback((node: ReferralNode) => {
     setTreeRootUser(node.accountSequence);