Fix ComparisonChart data display issue

The chart was not showing data because the API response format changed.
Fixed the calculation of PnL percentage by computing it from total_pnl
and balance values (initial_balance = balance - total_pnl).
Now the AI competition chart should properly display performance comparison data.
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: tinkle-community <tinklefund@gmail.com>

web/src/components/ComparisonChart.tsx

@@ -92,8 +92,13 @@ export function ComparisonChart({ traders }: ComparisonChartProps) {
           });
         }
 
+        // 计算盈亏百分比：从total_pnl和balance计算
+        // 假设初始余额 = balance - total_pnl
+        const initialBalance = point.balance - point.total_pnl;
+        const pnlPct = initialBalance > 0 ? (point.total_pnl / initialBalance) * 100 : 0;
+
         timestampMap.get(ts)!.traders.set(trader.trader_id, {
-          pnl_pct: point.total_pnl_pct,
+          pnl_pct: pnlPct,
           equity: point.total_equity
         });
       });