Add InsertNotificationAsync with explicit status/createdAt parameters so tests
can seed back-dated Retrying rows that satisfy the IsStuck derived property
(Status ∈ {Pending,Retrying} && CreatedAt < now − 10 min). Refactor
InsertParkedNotificationAsync to delegate to it, preserving its exact public
signature and producing identical SQL for existing callers.
Joseph Doherty