Add broadcaster subscription lifecycles

src/app.ts

@@ -1,5 +1,6 @@
 import { Config } from './services/config.ts';
 import { Database, MigrationService } from './services/storage/index.ts';
+import { Broadcaster } from './services/broadcaster.ts';
 import { ApplicationRouter } from './services/router.ts';
 import { Logger } from './utils/logger.ts';
 
@@ -18,6 +19,8 @@ export class App {
         const migrations = new MigrationService(database, debug);
         await migrations.migrateToLatest();
 
+        // Domain services are shared across all transports and route modules.
+        const broadcaster = new Broadcaster(debug);
         const routes = [];
 
         // Route loading is an explicit startup phase, not first-request work.
@@ -25,13 +28,14 @@ export class App {
         // before any client can connect.
         const router = await ApplicationRouter.create(routes);
 
-        return new App(database, router);
+        return new App(database, broadcaster, router);
     }
 
     private stopPromise: Promise<void> | undefined;
 
     constructor(
         private readonly database: Database,
+        private readonly broadcaster: Broadcaster,
         private readonly router: ApplicationRouter,
     ) {}