HR-Admin ERP Cloudflare POC

This is an isolated Pages Functions + D1 feasibility POC. It is not the production ERP.

• GET /api/poc/health
• GET /api/poc/items
• POST /api/poc/items with JSON {"code":"POC-1","name":"Item"}
• PATCH /api/poc/items/:id with JSON {"name":"Updated"}
• POST /api/poc/batch with JSON {"items":[...]}