refactor: add block cron to node client, but ensure it only runs on boot

src/node/client.ts

@@ -25,4 +25,14 @@ export default class Client extends BaseClient {
     this.beaconUrl = config.beaconUrl;
     this.http.defaults.baseURL = this.beaconUrl;
   }
+
+  async sync(): Promise<void> {
+    await super.sync();
+
+    if (!this.booted) {
+      this.subscribe();
+
+      this.booted = true;
+    }
+  }
 }