HEL-543: add data hub observability side-channel (provider status, source catalog, lineage)

- New provider_call_log/provider_health tables (additive-only schema),
  wired via a fail-open observability.observe()/record_call() helper.
- Tushare pipeline keeps its existing src_calls record unchanged and now
  also feeds the unified provider_health/provider_call_log side channel.
- Eastmoney/Tencent realtime_serve.py call sites and the iFinD steward
  call site are wrapped with observability.observe() at the call site
  only; no adapter internals, routing, fallback order, or return values
  are touched.
- New read-only admin API endpoints: /admin/api/providers/status,
  /admin/api/source-catalog, /admin/api/lineage,
  /admin/api/lineage/affected.
- New static, read-only source_catalog.py and lineage.py registries
  documenting existing providers/interfaces/datasets and known
  main-site consumers (cited against backend/features/screener and
  backend/features/heaven call sites).
- provider_call_log is purged by the existing pipeline.cleanup() job
  alongside src_calls/job_runs.
- 47 new unit/integration tests covering classification, fail-open
  behavior under DB/log failures, unchanged payloads/exceptions on
  success and failure paths, and the new HTTP endpoints. Full suite:
  173 tests, all green.

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

xiaobai-datahub/datahub/steward.py

@@ -12,6 +12,7 @@ from typing import Any
 
 from datahub.adapters.base import AdapterError
 from datahub.adapters.tushare import TUSHARE_FIELDS
+from datahub import observability
 from datahub.numbers import finite_number
 from datahub.realtime_serve import (
     RealtimeApiError,
@@ -152,8 +153,12 @@ def _ifind_query(api, api_name: str, params: dict[str, Any], fields: str) -> dic
         )
     if not adapter.configured:
         raise ApiError("SOURCE_UNAVAILABLE", "iFinD 尚未配置")
+    db = getattr(api, "db", None)
     try:
-        rows = adapter.fetch(dataset, dict(params))
+        rows = observability.observe(
+            db, "ifind", dataset, lambda: adapter.fetch(dataset, dict(params)),
+            classify=lambda r: observability.classify_rows(r, freshness_field=None),
+        )
     except AdapterError as exc:
         raise ApiError("SOURCE_UNAVAILABLE", str(exc)) from exc
     return envelope(