feat: add environment variable validation on backend startup

Author: emdevelopa

backend/src/index.ts

@@ -1,4 +1,15 @@
 import "dotenv/config";
+
+const REQUIRED_ENV_VARS = ["DATABASE_URL", "DIRECT_URL"];
+
+for (const key of REQUIRED_ENV_VARS) {
+  if (!process.env[key]) {
+    console.error(`[startup] Missing required environment variable: ${key}`);
+    console.error("Check backend/.env.example for the full list of required variables.");
+    process.exit(1);
+  }
+}
+
 import { app } from "./app.js";
 
 const port = Number(process.env.PORT ?? 4000);