032: fix final sync→async cascade (dataset_review, parsing, validation)

- _parsing.py: parse_superset_link + _recover_dataset_binding → async
    (await get_dashboard_detail, get_chart)
  - dataset_review/orchestrator.py: start_session + _build_recovery_bootstrap → async
    (await get_dataset_detail, parse_superset_link)
  - _routes.py (dataset_review): await orchestrator.start_session()
  - validation_tasks.py: await parse_superset_link + get_dashboard_detail

backend/src/api/routes/dataset_review_pkg/_routes.py

@@ -161,7 +161,7 @@ async def start_session(
             },
         )
         try:
-            result = orchestrator.start_session(
+            result = await orchestrator.start_session(
                 StartSessionCommand(
                     user=current_user,
                     environment_id=request.environment_id,

backend/src/api/routes/validation_tasks.py

@@ -412,7 +412,7 @@ async def parse_superset_url(
         from ...core.utils.superset_context_extractor import SupersetContextExtractor
 
         extractor = SupersetContextExtractor(environment=env)
-        parsed = extractor.parse_superset_link(payload.url)
+        parsed = await extractor.parse_superset_link(payload.url)
 
         dashboard_id = str(parsed.dashboard_id) if parsed.dashboard_id is not None else None
         title: str | None = None
@@ -420,7 +420,7 @@ async def parse_superset_url(
         # Resolve dashboard title from Superset API when possible
         if parsed.dashboard_id:
             try:
-                dashboard = extractor.client.get_dashboard_detail(parsed.dashboard_id)
+                dashboard = await extractor.client.get_dashboard_detail(parsed.dashboard_id)
                 title = dashboard.get("dashboard_title", str(parsed.dashboard_id))
             except Exception:
                 title = str(parsed.dashboard_id)