feat(backend): add SSE plugin with heartbeat interval for server events

Author: Lasim

package-lock.json

@@ -24,6 +24,7 @@
     "@fastify/cors": "^11.1.0",
     "@fastify/formbody": "^8.0.2",
     "@fastify/rate-limit": "^10.3.0",
+    "@fastify/sse": "^0.4.0",
     "@fastify/swagger": "^9.6.1",
     "@fastify/swagger-ui": "^5.2.3",
     "@lucia-auth/adapter-drizzle": "^1.1.0",

services/backend/package.json

@@ -2,6 +2,7 @@ import { FastifyInstance } from 'fastify'
 import fastifyCors from '@fastify/cors'
 import fastifyFormbody from '@fastify/formbody'
 import fastifyRateLimit from '@fastify/rate-limit'
+import fastifySSE from '@fastify/sse'
 
 export const registerFastifyPlugins = async (server: FastifyInstance): Promise<void> => {
   // Build allowed origins array
@@ -38,6 +39,12 @@ export const registerFastifyPlugins = async (server: FastifyInstance): Promise<v
   })
   server.log.info('Rate limiting plugin registered (per-route configuration enabled)');
 
+  // Register SSE (Server-Sent Events) plugin
+  await server.register(fastifySSE, {
+    heartbeatInterval: 30000 // Send heartbeat every 30 seconds to keep connections alive
+  })
+  server.log.info('SSE plugin registered (heartbeat interval: 30s)');
+
   // Favicon plugin is now registered in server.ts after Swagger to exclude it from documentation
 
   // Register other plugins as needed