Stage 78 — PWA School Identity & Contact

Adds a protected School Identity section to the PWA using the existing authenticated School Info API.
Shows school name, email, phone and status only; no usernames, passwords, tokens or other sensitive fields are exposed.
Adds refresh control and responsive styling.
Bumps service worker cache to v33 and preserves API/private-route exclusions.
No database changes.
Test: /school-management-system/upgrade/stage78.php
