STAGE 7 — SECURITY HARDENING

Upload this package over the working Stage 6 installation.

Test:
https://ieduportal.com/school-management-system/public/upgrade/stage7.php

Then test one normal login: Parent1 / Parent1.

Stage 7 adds security headers, strict session cookies, session fixation protection,
idle/absolute session timeout, and login throttling. It preserves Stage 6
plaintext-to-password_hash migration and existing dashboard routing.

Do not import SQL.
