fix: UPBIT_MARKETS 미사용 import 제거 후 기본값 KRW-BTC 하드코딩

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/components/BacktestHistoryPage.tsx

@@ -97,7 +97,7 @@ export function BacktestHistoryPage({ theme = 'dark' }: Props) {
   const [strategies, setStrategies] = useState<StrategyDto[]>([]);
 
   // ── 빠른 백테스팅 실행 ──────────────────────────────────────────────────────
-  const [runMarket, setRunMarket] = useState<string>(UPBIT_MARKETS[0]);
+  const [runMarket, setRunMarket] = useState<string>('KRW-BTC');
   const [runTimeframe, setRunTimeframe] = useState<Timeframe>('1D');
   const [runStrategyId, setRunStrategyId] = useState<number | null>(null);
   const [runLoading, setRunLoading] = useState(false);