feat(teacher): 在签到页面日期显示中添加星期几信息

 <!--
   * @Date: 2025-05-29 15:34:17
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2025-12-14 01:33:55
+ * @LastEditTime: 2025-12-14 22:37:25
  * @FilePath: /mlaj/src/views/teacher/checkinPage.vue
   * @Description: 文件描述
 -->
@@ -21,7 +21,7 @@
         <div class="bg-white px-4 py-3 flex items-center justify-between border-b border-gray-100 cursor-pointer" @click="showCalendar = true">
           <div class="flex items-center gap-2">
             <van-icon name="calendar-o" class="text-xl" color="#4caf50" />
-            <span style="color: #4caf50;" class="text-base font-bold">{{ formattedSelectedDate }}</span>
+            <span style="color: #4caf50;" class="text-base font-bold">{{ formattedSelectedDate }} {{ formattedWeekday }}</span>
           </div>
           <div class="flex items-center text-gray-400 text-sm">
             <span>切换日期</span>
@@ -172,6 +172,12 @@ const formattedSelectedDate = computed(() => {
   return dayjs(selectedDate.value).format('YYYY年MM月DD日');
 });
 
+// 计算属性：格式化星期几显示
+const formattedWeekday = computed(() => {
+    const weekdays = ['星期日', '星期一', '星期二', '星期三', '星期四', '星期五', '星期六']
+    return weekdays[dayjs(selectedDate.value).day()]
+})
+
 /**
  * 重置分页参数并重新加载数据
  */