style(views): 修改学生记录页面返回顶部按钮背景色

 <!--
  * @Date: 2025-11-19 22:05:00
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2025-12-13 21:42:55
+ * @LastEditTime: 2025-12-15 18:21:39
  * @FilePath: /mlaj/src/views/teacher/studentRecordPage.vue
  * @Description: 学生作业记录页面（仅作业记录与点评功能），固定 user_id 与 group_id
 -->
@@ -330,6 +330,9 @@ onBeforeUnmount(() => {
 </script>
 
 <style lang="less">
+.van-back-top {
+    background-color: #4caf50;
+}
 .comment-popup {
     .van-popup {
         max-width: 90vw;