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

backend/query-api/src/services/db.js

@@ -0,0 +1,72 @@
+import { Pool } from 'pg';
+
+let pool;
+
+function parseIntOrDefault(value, fallback) {
+  const parsed = Number.parseInt(`${value || fallback}`, 10);
+  return Number.isFinite(parsed) ? parsed : fallback;
+}
+
+function resolveDatabasePoolConfig() {
+  if (process.env.DATABASE_URL) {
+    return {
+      connectionString: process.env.DATABASE_URL,
+      max: parseIntOrDefault(process.env.DB_POOL_MAX, 10),
+      idleTimeoutMillis: parseIntOrDefault(process.env.DB_IDLE_TIMEOUT_MS, 30000),
+    };
+  }
+
+  const user = process.env.DB_USER;
+  const password = process.env.DB_PASSWORD;
+  const database = process.env.DB_NAME;
+  const host = process.env.DB_HOST || (
+    process.env.INSTANCE_CONNECTION_NAME
+      ? `/cloudsql/${process.env.INSTANCE_CONNECTION_NAME}`
+      : ''
+  );
+
+  if (!user || password == null || !database || !host) {
+    return null;
+  }
+
+  return {
+    host,
+    port: parseIntOrDefault(process.env.DB_PORT, 5432),
+    user,
+    password,
+    database,
+    max: parseIntOrDefault(process.env.DB_POOL_MAX, 10),
+    idleTimeoutMillis: parseIntOrDefault(process.env.DB_IDLE_TIMEOUT_MS, 30000),
+  };
+}
+
+export function isDatabaseConfigured() {
+  return Boolean(resolveDatabasePoolConfig());
+}
+
+function getPool() {
+  if (!pool) {
+    const resolved = resolveDatabasePoolConfig();
+    if (!resolved) {
+      throw new Error('Database connection settings are required');
+    }
+    pool = new Pool(resolved);
+  }
+  return pool;
+}
+
+export async function query(text, params = []) {
+  return getPool().query(text, params);
+}
+
+export async function checkDatabaseHealth() {
+  const result = await query('SELECT 1 AS ok');
+  return result.rows[0]?.ok === 1;
+}
+
+export async function closePool() {
+  if (pool) {
+    await pool.end();
+    pool = null;
+  }
+}