🐛 fix(exam): resolve classroom status and date display issues

- convert classroom status to number before comparison to fix status check logic
- correct date field name from training_date to trainingDate to display correct training date

src/client/mobile/components/Exam/ExamCard.tsx

@@ -56,7 +56,7 @@ export default function ExamCard() {
       return;
     }
     
-    if (classroomData && classroomData.status !== ClassroomStatus.OPEN) {
+    if (classroomData && Number(classroomData.status) !== ClassroomStatus.OPEN) {
       message.error('该教室已关闭');
       // globalThis.location.href = '/exam';
       navigate('/mobile')
@@ -277,7 +277,7 @@ export default function ExamCard() {
               <div className="text-blue-600">
                 <div className="mb-2">等待训练开始...</div>
                 <div className="text-sm text-gray-500">
-                  训练日期: {dayjs(classroomData.training_date).format('YYYY-MM-DD')}
+                  训练日期: {dayjs(classroomData.trainingDate).format('YYYY-MM-DD')}
                 </div>
               </div>
             )}