feat(nats): migrate to JetStream — at-least-once delivery with durable consumer

crates/worker/src/factory.rs

@@ -81,6 +81,9 @@ pub async fn build(
     let nats_client = async_nats::connect(nats_url)
         .await
         .expect("NATS connect failed");
+    nats::ensure_stream(&nats_client)
+        .await
+        .expect("JetStream stream setup failed");
     let consumer =
         event_transport::EventConsumerAdapter::new(nats::NatsMessageSource::new(nats_client));