Retry an alert webhook delivery event

Manually retry the delivery of a single alert webhook event. The event’s status is set to REPLAYING and a one-shot delivery attempt is scheduled on a dedicated retry queue. On completion, the event moves to DELIVERED (2XX response) or FAILED (non-2XX response or timeout).

Manual retries replace the automatic retry loop. If the target event is still PENDING, retrying it removes it from the normal automatic retry flow — the manual retry becomes the only remaining attempt. See Delivery event lifecycle for the full state machine.