feat: add healthz endpoint (#494)

frontend/src/routes/healthz/+server.ts

@@ -0,0 +1,18 @@
+import type { RequestHandler } from '@sveltejs/kit';
+import axios from 'axios';
+
+export const GET: RequestHandler = async () => {
+	const backendOK = await axios
+		.get(process!.env!.INTERNAL_BACKEND_URL + '/healthz')
+		.then(() => true, () => false);
+
+	return new Response(
+		backendOK ? `{"status":"HEALTHY"}` : `{"status":"UNHEALTHY"}`,
+		{
+			status: backendOK ? 200 : 500,
+			headers: {
+				'content-type': 'application/json'
+			}
+		}
+	);
+};