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/fetch/dart.py

@@ -0,0 +1,124 @@
+"""OpenDART 공시 본문 수집.
+
+키 없으면 SkippedMissingKey, 호출 측에서 skipped_missing_key 로 매핑.
+
+사용 endpoint:
+  - GET https://opendart.fss.or.kr/api/list.json    : 공시 목록 (기간/종목별)
+  - GET https://opendart.fss.or.kr/api/document.xml : 공시 원문 (zip in xml wrapper)
+
+여기서는 list.json만 받아서 title + url 만 저장. 본문 다운로드는 후속 단계에서
+선택적으로 추가 (용량/속도 트레이드오프).
+"""
+from __future__ import annotations
+
+import logging
+from dataclasses import dataclass
+from datetime import date, datetime
+from typing import Any
+
+import httpx
+from tenacity import retry, retry_if_exception_type, stop_after_attempt, wait_exponential
+
+from app.config import settings
+
+logger = logging.getLogger(__name__)
+
+DART_BASE = "https://opendart.fss.or.kr/api"
+USER_AGENT = "stock_chart_site/0.1 (+personal)"
+
+
+class SkippedMissingKey(RuntimeError):
+    pass
+
+
+@dataclass
+class Disclosure:
+    code: str           # corp 종목코드 (있을 경우)
+    title: str
+    url: str
+    published_at: datetime
+
+
+def _has_key() -> bool:
+    return bool(settings.dart_api_key)
+
+
+def _stock_code_to_corp_code_cache() -> dict[str, str]:
+    """종목코드(6자리) -> corp_code(8자리) 매핑.
+
+    실제 운영에서는 corpCode.xml.zip 을 받아서 캐시해야 하지만, list.json 은
+    종목코드(stock_code)도 직접 받기 때문에 우선 빈 매핑으로 둔다.
+    """
+    return {}
+
+
+@retry(
+    stop=stop_after_attempt(3),
+    wait=wait_exponential(multiplier=1, min=1, max=8),
+    retry=retry_if_exception_type((httpx.HTTPError, httpx.TimeoutException)),
+    reraise=True,
+)
+def fetch_disclosures(
+    code: str,
+    start: date,
+    end: date | None = None,
+    *,
+    page_count: int = 100,
+) -> list[Disclosure]:
+    """종목별 공시 목록 가져오기."""
+    if not _has_key():
+        raise SkippedMissingKey("dart api_key missing")
+    end = end or date.today()
+    params = {
+        "crtfc_key": settings.dart_api_key,
+        "bgn_de": start.strftime("%Y%m%d"),
+        "end_de": end.strftime("%Y%m%d"),
+        "page_count": str(page_count),
+        "stock_code": code,
+    }
+    with httpx.Client(timeout=15.0, headers={"User-Agent": USER_AGENT}) as cli:
+        resp = cli.get(f"{DART_BASE}/list.json", params=params)
+        resp.raise_for_status()
+        data = resp.json()
+
+    status = data.get("status")
+    # status: '000' OK, '013' no data, '020' rate limit, etc
+    if status == "013":
+        return []
+    if status and status != "000":
+        raise RuntimeError(f"dart error: status={status} msg={data.get('message')}")
+
+    out: list[Disclosure] = []
+    for row in data.get("list", []) or []:
+        rcept_no = row.get("rcept_no")
+        if not rcept_no:
+            continue
+        title = (row.get("report_nm") or "").strip()
+        url = f"https://dart.fss.or.kr/dsaf001/main.do?rcpNo={rcept_no}"
+        try:
+            published_at = datetime.strptime(row.get("rcept_dt", ""), "%Y%m%d")
+        except ValueError:
+            continue
+        out.append(
+            Disclosure(
+                code=row.get("stock_code") or code,
+                title=title,
+                url=url,
+                published_at=published_at,
+            )
+        )
+    return out
+
+
+def ping() -> dict[str, Any]:
+    if not _has_key():
+        return {"status": "skipped_missing_key"}
+    try:
+        # 어제 기준 1건만 조회 (sanity)
+        from datetime import timedelta
+        items = fetch_disclosures("005930", date.today() - timedelta(days=30), date.today(), page_count=1)
+        return {"status": "ok", "sample_count": len(items)}
+    except SkippedMissingKey:
+        return {"status": "skipped_missing_key"}
+    except Exception as exc:  # noqa: BLE001
+        return {"status": "failed", "error": str(exc)}