refactor: 重构页面路由结构与积分页面UI，优化列表交互体验

1. 重构路由结构：将班级子页移出ShellBranch，解决tabbar遮挡问题
2. 统一修改全局"没有更多了"提示文案为带品牌标识的版本
3. 重构积分排行榜UI，修复切换状态时的布局抖动问题，替换图标为CDN资源
4. 重构我的积分页面：对齐Vue端UI设计，新增展开收起详情功能，优化背景与布局
5. 优化我的互动页面布局与样式，新增背景图支持

lib/features/class/point_rank_view.dart

@@ -174,7 +174,11 @@ class _PointRankViewState extends ConsumerState<PointRankView> {
                   ? Colors.white
                   : Colors.white.withValues(alpha: 0.5),
               borderRadius: BorderRadius.circular(8.r),
-              border: active ? null : Border.all(color: Colors.white, width: 1),
+              // 始终保留 1px border 占位，避免激活/未激活切换时 content 区域差 2px 抖动
+              border: Border.all(
+                color: active ? Colors.transparent : Colors.white,
+                width: 1,
+              ),
             ),
             // Web 端回退字体行高偏大，固定高度可能溢出 → 内容放不下时自动缩小
             child: FittedBox(
@@ -190,7 +194,7 @@ class _PointRankViewState extends ConsumerState<PointRankView> {
                       color: active ? _primary : const Color(0xFF687FAD),
                     ),
                   ),
-                  SizedBox(height: 4.h),
+                  // SizedBox(height: 0.5.h),
                   Text(
                     '$countText人',
                     style: TextStyle(
@@ -202,7 +206,14 @@ class _PointRankViewState extends ConsumerState<PointRankView> {
               ),
             ),
           ),
-          if (active) _buildTriangle(),
+          // 始终渲染三角形占位，visible 切换避免外层 Column 高度变化抖动
+          Visibility(
+            visible: active,
+            maintainSize: true,
+            maintainAnimation: true,
+            maintainState: true,
+            child: _buildTriangle(),
+          ),
         ],
       ),
     );
@@ -338,11 +349,7 @@ class _PointRankViewState extends ConsumerState<PointRankView> {
                   ),
                 ),
                 SizedBox(width: 5.w),
-                Icon(
-                  _sortDesc ? Icons.arrow_downward : Icons.arrow_upward,
-                  size: 14,
-                  color: _primary,
-                ),
+                _buildSortIcons(),
               ],
             ),
           ),
@@ -351,6 +358,32 @@ class _PointRankViewState extends ConsumerState<PointRankView> {
     );
   }
 
+  Widget _buildSortIcons() {
+    final up = _sortDesc
+        ? '/StaticResource/2026-07-29/reverseOrder_up_icon1785291938907.png'
+        : '/StaticResource/2026-07-29/properOrder_up_icon1785291938906.png';
+    final down = _sortDesc
+        ? '/StaticResource/2026-07-29/reverseOrder_down_icon1785291938905.png'
+        : '/StaticResource/2026-07-29/properOrder_down_icon1785291938907.png';
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        CachedNetworkImage(
+          imageUrl: ImgUrl.build(up),
+          width: 12.w,
+          height: 7.h,
+          fit: BoxFit.contain,
+        ),
+        CachedNetworkImage(
+          imageUrl: ImgUrl.build(down),
+          width: 12.w,
+          height: 7.h,
+          fit: BoxFit.contain,
+        ),
+      ],
+    );
+  }
+
   Widget _buildMyRankCard() {
     final rank = _myRank!;
     return Container(