fix(HEL-164): 拒绝缓存不完整涨停快照

Co-authored-by: multica-agent <github@multica.ai>

backend/data/providers/tushare_dashboard.py

@@ -41,13 +41,16 @@ class DashboardMixin:
             raise TushareError(f"No daily data returned for {trade_date}")
 
         notices: list[str] = []
+        limit_data_source = "official"
         try:
             limit_rows = self._load_limit_lists(trade_date)
             previous_limit_rows = self._load_limit_type(previous_trade_date, "U")
             if not limit_rows:
+                limit_data_source = "derived"
                 notices.append("涨跌停高级接口当日数据尚未更新，已使用日线数据推算。")
                 limit_rows = self._derive_limits(trade_date, daily)
         except TushareError as exc:
+            limit_data_source = "derived"
             notices.append(f"涨跌停高级接口不可用，已使用日线数据推算：{exc}")
             limit_rows = self._derive_limits(trade_date, daily)
             previous_daily = self._load_daily(previous_trade_date)
@@ -79,6 +82,7 @@ class DashboardMixin:
                 "trade_date": _display_date(trade_date),
                 "previous_trade_date": _display_date(previous_trade_date),
                 "source": "tushare",
+                "limit_data_source": limit_data_source,
                 "updated_at": datetime.now().astimezone().isoformat(timespec="seconds"),
                 "notice": "；".join(notices),
             },