fix(admin-web): 仅在没有上级时显示总部节点

- 有上级时显示祖先节点列表
- 没有上级时才显示"总部"节点

🤖 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

@@ -413,14 +413,9 @@ export default function UserDetailPage() {
                   {/* 向上的引荐人链 */}
                   <div className={styles.referralTree__ancestors}>
                     <div className={styles.referralTree__label}>引荐人链 (向上)</div>
-                    {/* 总部节点（始终显示在最顶端） */}
-                    <div className={styles.referralTree__headquarters}>
-                      <span className={styles.referralTree__headquartersLabel}>总部</span>
-                    </div>
-                    <div className={styles.referralTree__connector}>↓</div>
-                    {/* 祖先节点列表 */}
-                    {referralTree.ancestors.length > 0 && (
+                    {referralTree.ancestors.length > 0 ? (
                       <>
+                        {/* 有上级时显示祖先节点列表 */}
                         <div className={styles.referralTree__nodeList}>
                           {referralTree.ancestors.map((ancestor, index) => (
                             <div key={ancestor.accountSequence} className={styles.referralTree__nodeWrapper}>
@@ -444,6 +439,14 @@ export default function UserDetailPage() {
                         </div>
                         <div className={styles.referralTree__connector}>↓</div>
                       </>
+                    ) : (
+                      <>
+                        {/* 没有上级时显示总部节点 */}
+                        <div className={styles.referralTree__headquarters}>
+                          <span className={styles.referralTree__headquartersLabel}>总部</span>
+                        </div>
+                        <div className={styles.referralTree__connector}>↓</div>
+                      </>
                     )}
                   </div>