feat(phase-1a): external data fetchers + refresh pipeline + scheduler

10종목 시드 + pykrx OHLCV / 외인·기관 거래대금, KIS read-only EOD, OpenDART
공시, 네이버 금융 뉴스 스크레이퍼, 구글 뉴스 RSS, yfinance 거시(KOSPI/KOSDAQ/
USDKRW/US10Y) fetcher 를 추가하고 refresh_one / daily_batch / backfill /
APScheduler(16:00 KST) 파이프라인으로 묶음.

- backend/app/seed: 10종목 시드 (대형/고변동/테마/플랫폼/방어)
- backend/app/fetch: pykrx, kis, dart, news, macro, symbols_seed
- backend/app/pipelines: refresh_one, daily_batch, backfill(CLI), scheduler
- backend/app/api/refresh.py: POST /api/refresh/{code}?lookback_days=N
- backend/app/main.py: lifespan 으로 스케줄러 기동/종료, /health/keys 추가
- README: .env 복사 안내 보강

스모크 테스트 (실제 키 사용) 결과:
  KIS token  : ok (token 346자 발급)
  KIS daily  : 005930 11rows
  DART list  : 005930 30일 10건
  Naver news : 005930 12건
  Google RSS : "삼성전자" 92건

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/app/api/refresh.py

@@ -0,0 +1,35 @@
+"""검증용 수동 갱신 API.
+
+POST /api/refresh/{code}
+  body: 없음
+  query: ?lookback_days=7 (기본)
+  resp:  refresh_one.RefreshReport.to_dict()
+"""
+from __future__ import annotations
+
+from fastapi import APIRouter, HTTPException, Query
+from sqlalchemy import text
+
+from app.db.connection import get_engine
+from app.pipelines.refresh_one import refresh_code
+
+router = APIRouter(prefix="/api", tags=["refresh"])
+
+
+def _resolve_name(code: str) -> str | None:
+    eng = get_engine()
+    with eng.connect() as conn:
+        row = conn.execute(text("SELECT name FROM symbols WHERE code = :code"), {"code": code}).first()
+    return row[0] if row else None
+
+
+@router.post("/refresh/{code}")
+def refresh_endpoint(
+    code: str,
+    lookback_days: int = Query(default=7, ge=1, le=365),
+) -> dict:
+    name = _resolve_name(code)
+    if not name:
+        raise HTTPException(status_code=404, detail=f"unknown code: {code} (symbols 테이블에 없음. 시드 필요)")
+    report = refresh_code(code, name, lookback_days=lookback_days)
+    return report.to_dict()