STAGE 53 — PWA UPDATE LIFECYCLE

Purpose:
- Adds a controlled PWA update lifecycle.
- New service-worker version is v5.
- New workers wait until the PWA shell explicitly requests activation.
- The PWA shell detects waiting updates and provides an Update now action.
- controllerchange reloads the shell once after activation.
- Existing offline recovery and public-only cache restrictions remain.

Deployment:
1. Upload this ZIP to the existing public deployment directory.
2. Do not import SQL.
3. Open /school-management-system/public/upgrade/stage53.php
4. Confirm all four checks show PASS.
5. Click Open PWA test shell.

No database/schema changes.
