feat(leaderboard): 下拉刷新动画图标

下拉刷新时顶部显示主题色旋转 spinner + "刷新中…"指示器,
仅下拉刷新显示(pullRefreshing),后台静默刷新保持无感。

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

pages/leaderboard/leaderboard.wxss

@@ -467,6 +467,39 @@
   color: var(--text-secondary);
 }
 
+/* 刷新中指示器:下拉刷新时顶部显示(后台静默刷新不显示,保持无感) */
+.refresh-indicator {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 10rpx;
+  padding: 14rpx 0;
+  animation: refreshFadeIn 0.2s ease;
+}
+
+.refresh-spinner {
+  width: 28rpx;
+  height: 28rpx;
+  border: 3rpx solid rgba(var(--primary-rgb), 0.2);
+  border-top-color: var(--primary);
+  border-radius: 50%;
+  animation: refreshSpin 0.8s linear infinite;
+}
+
+.refresh-text {
+  font-size: 24rpx;
+  color: var(--text-secondary);
+}
+
+@keyframes refreshSpin {
+  to { transform: rotate(360deg); }
+}
+
+@keyframes refreshFadeIn {
+  from { opacity: 0; }
+  to { opacity: 1; }
+}
+
 /* Loading: 旋转加载图标 + 骨架屏容器 */
 .leaderboard-skeleton {
   padding: 40rpx 32rpx 0;