refactor: optimize Dockerfile for multi-platform builds and add healthcheck script

healthcheck.js

@@ -0,0 +1,20 @@
+const http = require('http');
+
+const options = {
+  host: 'localhost',
+  port: 3000,
+  path: '/',
+  timeout: 2000,
+};
+
+const request = http.request(options, (res) => {
+  console.log(`HEALTHCHECK STATUS: ${res.statusCode}`);
+  process.exit(res.statusCode === 200 ? 0 : 1);
+});
+
+request.on('error', (err) => {
+  console.error('HEALTHCHECK ERROR', err);
+  process.exit(1);
+});
+
+request.end();