PinMe UniwebPay Payment Integration

Guides writing payment services in a PinMe Worker (Cloudflare Worker TypeScript) that call UniwebPay directly through @uniwebpay/sdk.

Core model: PinMe provisions the UniwebPay wallet and keys per PinMe user (not per project) and injects UNIWEB_* environment bindings at Worker deploy time; Worker code calls UniwebPay directly with the SDK — it does not go through PinMe payment proxy routes, and it must not call the legacy VibeCash APIs.