fix(HEL-412): 刷新降级不再整次失败，并补齐准备中提示

手动刷新与自动补跑共用可用数据判定：日线推算或上一交易日快照记为部分/准备中成功，避免前端误报刷新失败。HTTP JSON 解析错误不再把请求正文写入日志。

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

backend/data/datahub/bridge.py

@@ -25,6 +25,7 @@ EMPTY_FAIL_DATASETS = {"stocks", "daily", "index_daily", "valuation", "moneyflow
 
 
 def looks_like_heaven(module_name: str, filename: str = "") -> bool:
+    """问天调用栈识别。问天未永久冻结，只是本阶段仍走旧 Tushare 链路。"""
     path = filename.replace("\\", "/")
     return module_name.startswith("backend.features.heaven") or "/features/heaven/" in path
 
@@ -95,6 +96,7 @@ class DatahubBridge:
         legacy_query: Callable[..., list[dict[str, Any]]],
     ) -> list[dict[str, Any]]:
         dataset = API_TO_DATASET.get(api_name)
+        # 问天允许后续纳入 datahub；首批只读接入仍保持旧链路，避免误切。
         if not dataset or self.heaven_guard():
             return legacy_query(api_name, params, fields)
         flags = self.settings.flags(dataset)