feat(orderbook): 10단계 호가 패널 (KIS asking-price 스냅샷)

backend:
- fetch/kis.py: fetch_orderbook(code) — KIS FHKST01010200 (inquire-asking-price-exp-ccn)
  호출. output1 의 askp1~10/bidp1~10 + 잔량 + 합계, output2 의 현재가/전일대비 파싱.
- api/orderbook.py: GET /api/orderbook/{code}. symbols 매칭 안 되면 404, KIS 키 없으면
  skipped_missing_key 상태로 빈 호가 반환 (502 와 구분).
- main.py: orderbook_router 등록.

frontend:
- lib/api.ts: OrderbookResponse 타입 + api.orderbook(code).
- components/OrderbookPanel.tsx: 매도 10단계(위→아래 가격 내림차순) / 현재가(굵게, 전일대비)
  / 매수 10단계. 잔량 막대는 사이드별 max 정규화로 셀 안에서 자라남. ask=파랑, bid=빨강
  (한국 거래소 관행). 10초 폴링.
- app/[code]/page.tsx: 사이드바에 SymbolSidebar 다음으로 OrderbookPanel 마운트.

실시간 ws 가 아니라 HTTP 폴링이라 KIS rate-limit 친화적. 표시 전용 — 주문/체결 endpoint 는
일절 import 하지 않음 (kis.py 문서 정책).

backend/app/main.py

@@ -12,6 +12,7 @@ from app.api.chart import router as chart_router
 from app.api.markets import router as markets_router
 from app.api.metrics import router as metrics_router
 from app.api.news import router as news_router
+from app.api.orderbook import router as orderbook_router
 from app.api.predict import router as predict_router
 from app.api.refresh import router as refresh_router
 from app.api.symbols import router as symbols_router
@@ -106,6 +107,7 @@ app.include_router(metrics_router)
 app.include_router(news_router)
 app.include_router(markets_router)
 app.include_router(themes_router)
+app.include_router(orderbook_router)
 
 
 def _resolved_device() -> str: