refactor(stock): Phase 1 리뷰 반영 (public get_krx_tickers·타입·limit명명·테스트)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

stock/app/holdings_intel.py

@@ -8,13 +8,8 @@ from . import price_fetcher
 
 
 def _krx_tickers() -> set:
-    """krx_master에 존재하는 ticker 집합 (KRX 판별용)."""
-    with db._conn() as conn:
-        try:
-            rows = conn.execute("SELECT ticker FROM krx_master").fetchall()
-        except Exception:
-            return set()
-    return {r["ticker"] for r in rows}
+    """krx_master ticker 집합 (KRX 판별용)."""
+    return db.get_krx_tickers()
 
 
 def get_holdings() -> list[dict]: