fix(HEL-494): 日K默认45根并修复问天行业0/205覆盖

悬浮窗和详情页只画最近45个交易日，中枢仍保留250日历史。盘后缺sw_daily时保留成分日线内核，外显走免费申万；成分行情改为全市场快照+分页，不再截成前60只。

Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: multica-agent <github@multica.ai>

backend/features/market/service.py

@@ -1161,7 +1161,7 @@ class MarketServiceMixin:
             intraday_status = "unavailable"
             intraday_notice = "分时行情暂不可用，请稍后重试。"
 
-        prices = list(detail.get("prices") or [])[-60:]
+        prices = list(detail.get("prices") or [])[-DAILY_CHART_LIMIT:]
         stock = dict(detail.get("stock") or {"code": code})
         realtime = bool(detail_meta.get("realtime"))
         return {