fix: диагностика 502, /health и unit systemd для Caddy

Co-authored-by: Cursor <cursoragent@cursor.com>

src/routes/health.js

@@ -0,0 +1,15 @@
+const express = require('express');
+const { db } = require('../db');
+
+const router = express.Router();
+
+router.get('/health', (_req, res) => {
+  try {
+    db.prepare('SELECT 1').get();
+    res.json({ ok: true, service: 'shop' });
+  } catch (err) {
+    res.status(503).json({ ok: false, error: err.message });
+  }
+});
+
+module.exports = router;