考试限制IP，提交考试优化UI

src/features/OnlineExam/Examing/ExamingHome.vue

@@ -231,7 +231,11 @@ export default {
       });
     },
     async realSubmitPaper() {
-      this.$Spin.show();
+      this.$Spin.show({
+        render: () => {
+          return <div style="font-size: 50px">正在交卷，请耐心等待...</div>;
+        }
+      });
       this.toggleSnapNow();
       // 确保抓拍指令在交卷前执行
       setTimeout(() => this.realSubmitPaperStep2(), 1500);

src/features/OnlineExam/OnlineExamList.vue

@@ -67,6 +67,14 @@ export default {
       );
     },
     async enterExam(course) {
+      const ipLimit = (await this.$http.get(
+        "/api/ecs_exam_work/exam/ipLimit/" + course.examId
+      )).data;
+      if (ipLimit.limited) {
+        this.$Message.error("IP受限，请到中心指定地点进行考试！");
+        return;
+      }
+
       // TODO: 待确认. 前端控制展示“是否进入考试”。后端控制不在有效期内不准访问。
       if (course.faceEnable) {
         // open face check modal, then