feat: Introduce MessageBroker abstraction for decoupled event publishing, add notes-worker service, and optimize note repository tag fetching.

notes-api/src/nats_broker.rs

@@ -0,0 +1,31 @@
+//! NATS message broker adapter for domain MessageBroker port
+
+use async_trait::async_trait;
+use notes_domain::{DomainError, DomainResult, MessageBroker, Note};
+
+/// NATS adapter implementing the MessageBroker port
+pub struct NatsMessageBroker {
+    client: async_nats::Client,
+}
+
+impl NatsMessageBroker {
+    pub fn new(client: async_nats::Client) -> Self {
+        Self { client }
+    }
+}
+
+#[async_trait]
+impl MessageBroker for NatsMessageBroker {
+    async fn publish_note_updated(&self, note: &Note) -> DomainResult<()> {
+        let payload = serde_json::to_vec(note).map_err(|e| {
+            DomainError::RepositoryError(format!("Failed to serialize note: {}", e))
+        })?;
+
+        self.client
+            .publish("notes.updated", payload.into())
+            .await
+            .map_err(|e| DomainError::RepositoryError(format!("Failed to publish event: {}", e)))?;
+
+        Ok(())
+    }
+}