feat(backend): implement v2 domain slice and live smoke

backend/query-api/src/routes/health.js

@@ -1,4 +1,5 @@
 import { Router } from 'express';
+import { checkDatabaseHealth, isDatabaseConfigured } from '../services/db.js';
 
 export const healthRouter = Router();
 
@@ -13,3 +14,32 @@ function healthHandler(req, res) {
 
 healthRouter.get('/health', healthHandler);
 healthRouter.get('/healthz', healthHandler);
+
+healthRouter.get('/readyz', async (req, res) => {
+  if (!isDatabaseConfigured()) {
+    return res.status(503).json({
+      ok: false,
+      service: 'krow-query-api',
+      status: 'DATABASE_NOT_CONFIGURED',
+      requestId: req.requestId,
+    });
+  }
+
+  try {
+    const ok = await checkDatabaseHealth();
+    return res.status(ok ? 200 : 503).json({
+      ok,
+      service: 'krow-query-api',
+      status: ok ? 'READY' : 'DATABASE_UNAVAILABLE',
+      requestId: req.requestId,
+    });
+  } catch (error) {
+    return res.status(503).json({
+      ok: false,
+      service: 'krow-query-api',
+      status: 'DATABASE_UNAVAILABLE',
+      details: { message: error.message },
+      requestId: req.requestId,
+    });
+  }
+});