feat: set up app

Backend/index.ts

@@ -1 +1,11 @@
-console.log("Hello via Bun!");
+import express from 'express';
+
+const app = express();
+
+app.get('/', (req, res) => {
+  res.send('Hello World');
+});
+
+app.listen(3000, () => {
+  console.log('Server is running on port 3000');
+});