fix(HEL-487): 盘中当天看板在 rt_k 无权限时降级到免费实时源

rt_k 失败、无权限、超时或空结果时改用东财全市场快照，再失败则用腾讯批量行情；两者都失败仍不退回昨天。

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

backend/features/market/service.py

@@ -63,7 +63,11 @@ class MarketServiceMixin:
         if gateway is not None:
             return gateway.tushare()
         # Compatibility for isolated legacy unit-test service stubs.
-        return TushareClient(self.token)
+        client = TushareClient(self.token)
+        aggregator = getattr(self, "realtime_aggregator", None)
+        if aggregator is not None:
+            client.realtime_aggregator = aggregator
+        return client
 
     def _now(self) -> datetime:
         clock = getattr(self, "clock", None)
@@ -289,7 +293,10 @@ class MarketServiceMixin:
                     raise TushareError("公共行情尚未配置")
                 dashboard = self._tushare_client().dashboard(normalized_date)
                 meta = dashboard.setdefault("meta", {})
+                quote_source = str(meta.get("quote_source") or "")
                 meta["source"] = source
+                if quote_source:
+                    meta["quote_source"] = quote_source
                 meta["requested_date"] = self._display_compact_date(normalized_date)
                 if meta.get("limit_data_source") == "derived":
                     meta.setdefault(