feat(health): /api/health/services (grouped+counts) + owner /check

Adds GET /api/health/services returning registry services grouped by
category with merged cached status and per-group healthy counts, and
POST /api/health/check (owner-only) that enqueues a health.check
pg-boss job. Registers the health_check worker in the jobs index.

lib/jobs/workers/health_check.js

@@ -0,0 +1,8 @@
+import { load } from '../../health/registry.js';
+import { checkAll } from '../../health/checker.js';
+import * as statusRepo from '../../db/repos/service_status.js';
+export const NAME = 'health.check';
+export async function handler(_job) {
+  const results = await checkAll(load());
+  for (const r of results) await statusRepo.upsert(r);
+}