fix(leaderboard): 修复加载期空白页,加 loading 图标

- leaderboard.json 未注册 ui-skeleton,骨架屏不渲染致 loading 期空白
- 注册 ui-skeleton,骨架屏恢复 shimmer
- 骨架屏上方加主题色旋转加载图标 + "加载中…"

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

pages/leaderboard/leaderboard.json

@@ -1,5 +1,7 @@
 {
   "navigationBarTitleText": "排行榜",
   "enablePullDownRefresh": true,
-  "usingComponents": {}
+  "usingComponents": {
+    "ui-skeleton": "../../components/ui-skeleton/ui-skeleton"
+  }
 }

pages/leaderboard/leaderboard.wxml

@@ -12,8 +12,12 @@
     </view>
   </view>
 
-  <!-- Loading skeleton -->
+  <!-- Loading: 旋转加载图标 + 骨架屏 -->
   <view class="leaderboard-skeleton" wx:if="{{loading}}">
+    <view class="lb-loading">
+      <view class="lb-loading__spinner"></view>
+      <text class="lb-loading__text">加载中…</text>
+    </view>
     <ui-skeleton variant="list-row" count="{{5}}" />
   </view>
 

pages/leaderboard/leaderboard.wxss

@@ -427,3 +427,34 @@
   font-size: 26rpx;
   color: var(--text-secondary);
 }
+
+/* Loading: 旋转加载图标 + 骨架屏容器 */
+.leaderboard-skeleton {
+  padding: 40rpx 32rpx 0;
+}
+
+.lb-loading {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 20rpx;
+  padding: 24rpx 0 48rpx;
+}
+
+.lb-loading__spinner {
+  width: 56rpx;
+  height: 56rpx;
+  border: 4rpx solid rgba(var(--primary-rgb), 0.15);
+  border-top-color: var(--primary);
+  border-radius: 50%;
+  animation: lbSpin 0.8s linear infinite;
+}
+
+.lb-loading__text {
+  font-size: 26rpx;
+  color: var(--text-secondary);
+}
+
+@keyframes lbSpin {
+  to { transform: rotate(360deg); }
+}