feat(HEL-490): 剩余行情改由数据中枢主线路提供

正式页面以 8766 为主线路，旧接口只作故障备用；compose 钉死全部 DATAHUB_READ_*，避免现网残留 0 造成假完成。

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

backend/features/system/service.py

@@ -130,6 +130,7 @@ class SystemServiceMixin:
                 ),
                 **self.database.status(),
                 "jobs": self.jobs.repository.recent(12),
+                "datahub": self._datahub_status(),
             },
             "llm": {
                 "primary_configured": self._profile_configured(platform["primary"]),
@@ -145,6 +146,22 @@ class SystemServiceMixin:
             },
         }
 
+    def _datahub_status(self) -> dict[str, Any]:
+        gateway = getattr(self, "data_gateway", None)
+        reporter = getattr(gateway, "datahub_status", None)
+        if callable(reporter):
+            return reporter()
+        return {
+            "configured": False,
+            "base_url": "",
+            "enabled_reads": 0,
+            "total_reads": 0,
+            "flags": [],
+            "routes": [],
+            "fallback_count": 0,
+            "fallback_labels": [],
+        }
+
     def save_system_settings(self, payload: dict[str, Any]) -> dict[str, Any]:
         current = dict(self._system_credentials)
         token = str(payload.get("tushare_token") or current.get("tushare_token") or "").strip()