feat(stock): GET /api/stock/holidays endpoint (SP-10 task-watcher용)

holidays.json(list) 노출. task-watcher가 휴장일 판정에 조회.
인증 불필요. 주말은 task-watcher가 weekday로 별도 판정.
Plan-B-Infra Phase 1.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

stock/app/main.py

@@ -162,6 +162,17 @@ def get_indices():
     """주요 지표(KOSPI 등) 실시간 크롤링 조회"""
     return fetch_major_indices()
 
+@app.get("/api/stock/holidays")
+def get_holidays():
+    """task-watcher가 조회하는 휴장일 목록. holidays.json(list) 노출 (인증 불필요)."""
+    try:
+        with open(_HOLIDAYS_PATH, encoding="utf-8") as f:
+            data = json.load(f)
+        holidays = data if isinstance(data, list) else []
+    except (OSError, ValueError):
+        holidays = []
+    return {"holidays": holidays}
+
 @app.post("/api/stock/scrap")
 def trigger_scrap():
     """수동 스크랩 트리거"""

stock/app/test_holidays_endpoint.py

@@ -0,0 +1,22 @@
+"""GET /api/stock/holidays — task-watcher 휴장일 조회용."""
+from fastapi.testclient import TestClient
+from app.main import app
+
+client = TestClient(app)
+
+
+def test_holidays_returns_list():
+    r = client.get("/api/stock/holidays")
+    assert r.status_code == 200
+    data = r.json()
+    assert "holidays" in data
+    assert isinstance(data["holidays"], list)
+
+
+def test_holidays_entries_are_iso_dates():
+    r = client.get("/api/stock/holidays")
+    holidays = r.json()["holidays"]
+    if holidays:
+        import datetime as dt
+        for h in holidays[:5]:
+            dt.date.fromisoformat(h)   # raise 안 하면 통과