🐛 fix(exam): 修复考试卡片交易记录显示问题

- 修改持仓股票显示逻辑，将数字"1"转换为"买入"文本
- 修改持仓现金显示逻辑，将数字"1"转换为"卖出"文本
- 添加dailyIncrease状态变量，初始化为"0.00%"

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

@@ -358,8 +358,8 @@ export default function ExamCard() {
             {[...answerRecords].reverse().map((record: AnswerRecord) => (
               <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>
+                <div className="text-red-500">{record.holdingStock === '1' ? '买入' : ''}</div>
+                <div className="text-green-500">{record.holdingCash === '1' ? '卖出' : ''}</div>
                 <div>{record.price}</div>
                 <div className={record.profitAmount >= 0 ? 'text-red-500' : 'text-green-500'}>
                   {record.profitAmount.toFixed(2)}