feat(arrival_statistics): 增加课程状态标签并优化显示逻辑

- 在课程未开始时添加"未开始"标签
-调整"已结束"标签的显示条件，仅在状态为2时显示
- 优化课程状态的判断逻辑，提高代码可读性

pages/coach/my/arrival_statistics.vue

@@ -36,8 +36,10 @@
               </view>
             </view>
             <view class="right_box">
+              <view v-if="!(['1','2'].includes(String(v.status)))" class="tag" style="background:#20CAAF;">未开始</view>
+
               <view v-if="v.status == 1" class="tag" style="background:#fad24e;">上课中</view>
-              <view v-else class="tag" style="background:#e2e2e2;">已结束</view>
+              <view v-if="v.status == 2" class="tag" style="background:#e2e2e2;">已结束</view>
             </view>
           </view>
         </view>