iEduPortal Stage 9 - REST API v1 foundation

Endpoint:
  /api/v1/health.php

Purpose:
  Provides a read-only JSON health check for the future mobile/native API.

This stage does NOT:
  - change the database schema
  - change existing login pages
  - issue API access tokens
  - expose student, parent, staff, fee, or academic data

Expected successful response:
  {"success":true,"api":"ieduportal","version":"v1","status":"ok","database":"ok"}

Do not expose database credentials or internal errors through the API.
