feat(health): service_status cache table + repo

lib/db/migrations/014_service_status.sql

@@ -0,0 +1,8 @@
+-- 014_service_status.sql
+CREATE TABLE service_status (
+  service_id  text PRIMARY KEY,
+  status      text NOT NULL CHECK (status IN ('ok','warn','down','unknown')),
+  latency_ms  integer,
+  detail      text,
+  checked_at  timestamptz NOT NULL DEFAULT now()
+);

lib/db/repos/service_status.js

@@ -0,0 +1,14 @@
+import { pool } from '../pool.js';
+export async function upsert({ service_id, status, latency_ms = null, detail = null }) {
+  await pool.query(
+    `INSERT INTO service_status (service_id, status, latency_ms, detail, checked_at)
+     VALUES ($1,$2,$3,$4, now())
+     ON CONFLICT (service_id) DO UPDATE
+       SET status=EXCLUDED.status, latency_ms=EXCLUDED.latency_ms,
+           detail=EXCLUDED.detail, checked_at=now()`,
+    [service_id, status, latency_ms, detail]);
+}
+export async function all() {
+  const { rows } = await pool.query(`SELECT * FROM service_status`);
+  return rows;
+}