feat(jobs): pg-boss singleton client

Per-name ensureQueue promise dedup so concurrent enqueue+subscribe
on the same queue do not race createQueue (Postgres deadlock).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/helpers/boss.js

@@ -0,0 +1,23 @@
+import * as queue from '../../lib/jobs/queue.js';
+import { pool } from '../../lib/db/pool.js';
+
+export async function stopBoss() {
+  try { await queue.stop(); } catch { /* ignore */ }
+  try { await pool.query('DROP SCHEMA IF EXISTS pgboss CASCADE'); } catch { /* ignore */ }
+}
+
+export async function waitForJob(id, { timeoutMs = 5_000 } = {}) {
+  const boss = queue.instance();
+  if (!boss) throw new Error('queue not started');
+  const start = Date.now();
+  while (Date.now() - start < timeoutMs) {
+    const j = await boss.getJobById(id);
+    if (!j) {
+      await new Promise(r => setTimeout(r, 50));
+      continue;
+    }
+    if (['completed','failed','cancelled','expired'].includes(j.state)) return j;
+    await new Promise(r => setTimeout(r, 50));
+  }
+  throw new Error(`job ${id} did not finish in ${timeoutMs} ms`);
+}

tests/jobs/queue.test.js

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+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { resetDb } from '../helpers/db.js';
+import { migrateUp } from '../../lib/db/migrate.js';
+import { stopBoss } from '../helpers/boss.js';
+import * as queue from '../../lib/jobs/queue.js';
+
+beforeEach(async () => { await resetDb(); await migrateUp(); });
+afterEach(async () => { await stopBoss(); });
+
+describe('jobs/queue', () => {
+  it('starts, enqueues, and a worker receives the job', async () => {
+    await queue.start();
+    const received = new Promise(resolve => {
+      queue.subscribe('echo-q', async job => { resolve(job.data); });
+    });
+    const jobId = await queue.enqueue('echo-q', { hello: 'void' });
+    expect(jobId).toBeTruthy();
+    const data = await received;
+    expect(data).toEqual({ hello: 'void' });
+  });
+});