💄 style(exam): 优化考试卡片表格显示

- 调整表格列布局，从7列改为6列，移除重复的"号"列
- 修改表头"序"为更清晰的"序号"
- 移除表格内容中重复显示的index值
- 保持表格整体布局紧凑，提升数据可读性

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

@@ -344,20 +344,19 @@ export default function ExamCard() {
           </div>
 
           {/* 表格头部 */}
-          <div className="grid grid-cols-7 gap-4 py-2 border-b border-gray-200 text-sm font-medium text-gray-600">
-            <div>序</div>
+          <div className="grid grid-cols-6 gap-4 py-2 border-b border-gray-200 text-sm font-medium text-gray-600">
+            <div>序号</div>
             <div>持股</div>
             <div>持币</div>
             <div>价格</div>
             <div>收益(元)</div>
             <div>盈亏率</div>
-            <div>号</div>
           </div>
 
           {/* 表格内容 */}
           <div className="max-h-60 overflow-y-auto">
             {[...answerRecords].reverse().map((record: AnswerRecord) => (
-              <div key={record.date} className="grid grid-cols-7 gap-4 py-2 text-sm text-gray-800 hover:bg-gray-50">
+              <div key={record.date} className="grid grid-cols-6 gap-4 py-2 text-sm text-gray-800 hover:bg-gray-50">
                 <div>{record.index}</div>
                 <div className="text-red-500">{record.holdingStock}</div>
                 <div className="text-green-500">{record.holdingCash}</div>
@@ -368,7 +367,6 @@ export default function ExamCard() {
                 <div className={record.profitPercent >= 0 ? 'text-red-500' : 'text-green-500'}>
                   {record.profitPercent.toFixed(2)}%
                 </div>
-                <div>{record.index}</div>
               </div>
             ))}
           </div>