feat: update backend src/index.ts with basic Fastify server

backend/src/index.ts

@@ -1,15 +1,19 @@
-import app from './server.js';
+import fastify from 'fastify'
 
-const PORT = process.env.PORT ? parseInt(process.env.PORT, 10) : 3001;
+const app = fastify({ logger: true })
+
+app.get('/api/health', async (request, reply) => {
+  return { status: 'OK' }
+})
 
 const start = async () => {
   try {
-    await app.listen({ port: PORT, host: '0.0.0.0' });
-    console.log(`Server listening on port ${PORT}`);
+    await app.listen({ port: 3001, host: '0.0.0.0' })
+    console.log('Server listening on port 3001')
   } catch (err) {
-    app.log.error(err);
-    process.exit(1);
+    app.log.error(err)
+    process.exit(1)
   }
-};
+}
 
-start();
+start()