fix(HEL-494): 网站市场客户端改为纯中枢 Facade，并迁移 iFinD 凭据到中枢

生产 gateway 不再读取 Tushare token 或实例化 TushareProvider/TushareClient；问财凭据经带鉴权的中枢接口加密入库，避免发版后 iFinD 未配置。

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

backend/application.py

@@ -125,6 +125,10 @@ class DashboardService(
         )
         self.data_gateway = self.container.data_gateway
         self.ifind = self.container.ifind
+        refresh = str(self._system_credentials.get("ifind_refresh_token") or "")
+        access = str(self._system_credentials.get("ifind_access_token") or "")
+        if refresh or access:
+            self.ifind.set_credentials(refresh, access)
         self.screener = self.container.screener
         self.strategy_tracking = self.container.strategy_tracking
         self.alert_service = self.container.alert_service