fix: 네이버 차트 폴백 null/0 가격 필터링

Lightweight Charts에서 null 값 에러 방지

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/api/endpoints/market_data.py

@@ -334,17 +334,24 @@ async def get_chart_data_cached(stock_code: str, period: str, limit: int) -> lis
             from app.services.naver_finance import get_naver_daily_chart
             naver_data = await get_naver_daily_chart(stock_code, days=limit * 2)
             if naver_data:
-                db_data = [
-                    {
-                        "date": item.get("stck_bsop_date", ""),
-                        "open": float(item.get("stck_oprc", 0)),
-                        "high": float(item.get("stck_hgpr", 0)),
-                        "low": float(item.get("stck_lwpr", 0)),
-                        "close": float(item.get("stck_clpr", 0)),
-                        "volume": int(item.get("acml_vol", 0)),
-                    }
-                    for item in naver_data
-                ][-limit:]
+                db_data = []
+                for item in naver_data:
+                    o = float(item.get("stck_oprc") or 0)
+                    h = float(item.get("stck_hgpr") or 0)
+                    l = float(item.get("stck_lwpr") or 0)
+                    c = float(item.get("stck_clpr") or 0)
+                    d = item.get("stck_bsop_date", "")
+                    if not d or c <= 0 or o <= 0 or h <= 0 or l <= 0:
+                        continue
+                    db_data.append({
+                        "date": d,
+                        "open": o,
+                        "high": h,
+                        "low": l,
+                        "close": c,
+                        "volume": int(item.get("acml_vol") or 0),
+                    })
+                db_data = db_data[-limit:]
                 logger.info(f"차트 네이버 폴백: {stock_code} ({len(db_data)}행)")
         except Exception as e:
             logger.warning(f"네이버 차트 폴백 실패 ({stock_code}): {e}")