feat: 移除回测交易记录的盈亏列

- 移除盈亏列，进一步简化交易记录表格
- 盈亏信息已在统计卡片和图表中展示

frontend/src/pages/BacktestDetail.tsx

@@ -232,22 +232,6 @@ const BacktestDetail: React.FC = () => {
       width: 120,
       render: (value: string) => formatUSDC(value)
     },
-    {
-      title: t('backtest.profitLoss') + ' (USDC)',
-      dataIndex: 'profitLoss',
-      key: 'profitLoss',
-      width: 120,
-      render: (value: string | null) => {
-        if (!value) return '-'
-        const num = parseFloat(value)
-        const color = num > 0 ? '#52c41a' : num < 0 ? '#ff4d4f' : undefined
-        return (
-          <span style={{ color }}>
-            {formatUSDC(value)}
-          </span>
-        )
-      }
-    },
     {
       title: t('backtest.balanceAfter') + ' (USDC)',
       dataIndex: 'balanceAfter',