refactor: simplify task and history services

Remove retired query paths and repository compatibility branches, and share task test fixtures.
Cancel pending questions and resolve their notifications when recovering expired runs.

app/services/task_questions.py

@@ -13,9 +13,7 @@ if TYPE_CHECKING:
 
 
 async def list_questions(service: "OperationalTaskService", task_id: UUID) -> list[dict]:
-    # Legacy test repositories do not implement question persistence.
-    reader = getattr(service.repo, "list_questions", None)
-    return await reader(str(task_id)) if reader else []
+    return await service.repo.list_questions(str(task_id))
 
 
 async def cancel_pending(service: "OperationalTaskService", task_id: UUID, now: datetime) -> None: