Refresh update check on page load when cache is stale

[veniplex]

Summary

Follow-up to #5. The daily cron (check-updates pg-boss job, 0 6 * * *) already keeps system.updateCheck fresh, so most page loads just read the cached setting — no outbound request.

As a backstop for when the cron missed its run (e.g. the server was down at 06:00), getUpdateStatus() now schedules one background GitHub check via Next.js's after() (runs after the response is sent, doesn't block the page) whenever the cached result is older than 20 hours. Concurrent requests during that window are deduped via an in-process in-flight guard, so several tabs/admins loading a page at once while the cache is stale only trigger one outbound request.

Net effect: on login or a full page reload, an admin sees a check that's at most ~20h old, refreshing itself in the background if it's gone stale — without hitting GitHub's API on every request.

Test plan

• npx tsc --noEmit
• npx eslint src/lib/update-check.ts
• npx prettier --check src/lib/update-check.ts
• Manual QA: with an old checkedAt in system.updateCheck, confirm a page load triggers exactly one refresh (check server logs / the setting's checkedAt updates)

---

Generated by Claude Code