feat(backend): add isolated v2 foundation stack and query service scaffold

backend/query-api/test/app.test.js

@@ -0,0 +1,24 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import request from 'supertest';
+import { createApp } from '../src/app.js';
+
+test('GET /healthz returns healthy response', async () => {
+  const app = createApp();
+  const res = await request(app).get('/healthz');
+
+  assert.equal(res.status, 200);
+  assert.equal(res.body.ok, true);
+  assert.equal(res.body.service, 'krow-query-api');
+  assert.equal(typeof res.body.requestId, 'string');
+  assert.equal(typeof res.headers['x-request-id'], 'string');
+});
+
+test('GET unknown route returns not found envelope', async () => {
+  const app = createApp();
+  const res = await request(app).get('/query/unknown');
+
+  assert.equal(res.status, 404);
+  assert.equal(res.body.code, 'NOT_FOUND');
+  assert.equal(typeof res.body.requestId, 'string');
+});