feat(admin-web): 优化引荐关系树展示

- "认种"改名为"本人认种"
- 直推下级默认收起状态
- 有直推下级时在当前用户节点下方显示"+"按钮
- 点击"+"展开显示直推下级，按钮变为"-"
- 点击"-"收起直推下级

🤖 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

@@ -139,6 +139,7 @@ export default function UserDetailPage() {
   const [treeRootUser, setTreeRootUser] = useState<string>(accountSequence);
   const [plantingPage, setPlantingPage] = useState(1);
   const [walletPage, setWalletPage] = useState(1);
+  const [showDirectReferrals, setShowDirectReferrals] = useState(false); // 默认收起直推下级
 
   // 获取用户完整信息
   const { data: userDetail, isLoading: detailLoading, error: detailError } = useUserFullDetail(accountSequence);
@@ -356,7 +357,7 @@ export default function UserDetailPage() {
                                 {ancestor.nickname || '未设置'}
                               </span>
                               <span className={styles.referralTree__nodeAdoptions}>
-                                认种: {formatNumber(ancestor.personalAdoptions)}
+                                本人认种: {formatNumber(ancestor.personalAdoptions)}
                               </span>
                             </button>
                             {index < referralTree.ancestors.length - 1 && (
@@ -386,16 +387,25 @@ export default function UserDetailPage() {
                         {referralTree.currentUser.nickname || '未设置'}
                       </span>
                       <span className={styles.referralTree__nodeAdoptions}>
-                        认种: {formatNumber(referralTree.currentUser.personalAdoptions)}
+                        本人认种: {formatNumber(referralTree.currentUser.personalAdoptions)}
                       </span>
                       <span className={styles.referralTree__nodeCount}>
                         引荐: {formatNumber(referralTree.currentUser.directReferralCount)}
                       </span>
                     </div>
+                    {/* 展开/收起直推下级按钮 */}
+                    {referralTree.directReferrals.length > 0 && (
+                      <button
+                        className={styles.referralTree__toggleButton}
+                        onClick={() => setShowDirectReferrals(!showDirectReferrals)}
+                      >
+                        {showDirectReferrals ? '−' : '+'}
+                      </button>
+                    )}
                   </div>
 
-                  {/* 引荐用户 */}
-                  {referralTree.directReferrals.length > 0 && (
+                  {/* 引荐用户 - 默认收起，点击展开 */}
+                  {referralTree.directReferrals.length > 0 && showDirectReferrals && (
                     <div className={styles.referralTree__directReferrals}>
                       <div className={styles.referralTree__connector}>↓</div>
                       <div className={styles.referralTree__label}>
@@ -413,7 +423,7 @@ export default function UserDetailPage() {
                               {referral.nickname || '未设置'}
                             </span>
                             <span className={styles.referralTree__nodeAdoptions}>
-                              认种: {formatNumber(referral.personalAdoptions)}
+                              本人认种: {formatNumber(referral.personalAdoptions)}
                             </span>
                             {referral.directReferralCount > 0 && (
                               <span className={styles.referralTree__nodeCount}>

frontend/admin-web/src/app/(dashboard)/users/[id]/user-detail.module.scss

@@ -345,7 +345,31 @@
 }
 
 .referralTree__current {
-  @include flex-center;
+  @include flex-column;
+  align-items: center;
+}
+
+.referralTree__toggleButton {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 28px;
+  height: 28px;
+  margin-top: $spacing-sm;
+  background-color: $primary-color;
+  color: white;
+  border: none;
+  border-radius: 50%;
+  cursor: pointer;
+  font-size: 18px;
+  font-weight: bold;
+  line-height: 1;
+  @include transition-fast;
+
+  &:hover {
+    background-color: darken($primary-color, 10%);
+    transform: scale(1.1);
+  }
 }
 
 .referralTree__node {