refactor: code smell fixes — tests, events, naming

- Tests for ExecutePipelineHandler (happy path, fallback, disabled skip, failure retry, not found)
- Tests for ProcessNextJobHandler (empty queue, process, drain multiple)
- DerivativeGenerated domain event + event-payload mapping + event_store aggregate
- Renamed event-payload → adapters-event-payload, event-transport → adapters-event-transport

crates/bootstrap/src/factory.rs

@@ -22,12 +22,13 @@ pub async fn build_app(config: &Config) -> Result<Router> {
     adapters_nats::ensure_stream(&nats_client).await?;
 
     let transport = adapters_nats::NatsTransport::new(nats_client);
-    let nats_publisher: Arc<dyn domain::ports::EventPublisher> =
-        Arc::new(event_transport::EventPublisherAdapter::new(transport));
+    let nats_publisher: Arc<dyn domain::ports::EventPublisher> = Arc::new(
+        adapters_event_transport::EventPublisherAdapter::new(transport),
+    );
     let event_store: Arc<dyn domain::ports::EventStore> =
         Arc::new(adapters_postgres::PostgresEventStore::new(pool.clone()));
     let event_publisher: Arc<dyn domain::ports::EventPublisher> = Arc::new(
-        event_transport::CompositeEventPublisher::new(nats_publisher, event_store),
+        adapters_event_transport::CompositeEventPublisher::new(nats_publisher, event_store),
     );
 
     let storage_path = std::env::var("STORAGE_PATH").unwrap_or_else(|_| "./data/media".to_string());