feat(HEL-402): 接通网站首批只读 datahub 并建立双路对比

默认全部读取/影子开关关闭，网站继续走旧 Tushare 链路；开启单项时只替换该类原料并在失败时回旧，问天保持旧路径。

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

tests/test_data_gateway.py

@@ -67,6 +67,9 @@ class DataGatewayTests(unittest.TestCase):
             "TushareClient": {"backend/features/market/service.py"},
             "TushareProvider": {"backend/data/gateway.py"},
             "WebRealtimeAggregator": {"backend/data/gateway.py"},
+            "DatahubClient": {"backend/data/gateway.py"},
+            "DatahubAwareTushareClient": {"backend/data/gateway.py"},
+            "DatahubBridge": {"backend/data/gateway.py"},
         }
         found = {name: set() for name in owners}
         for path in (root / "backend").rglob("*.py"):