Function enqueue_critical 

pub async fn enqueue_critical<T>(
    client: &BackfillClient,
    task_identifier: &str,
    payload: &T,
    job_key: Option<String>,
) -> Result<EnqueueOutcome, BackfillError>
where
    T: Serialize,

Enqueue a critical job with aggressive exponential backoff retries.

Best for critical jobs that must succeed (12 attempts, up to 4 hour delays).