Build Bitcoin Payment Integration for E-commerce Platform

We need an experienced developer to integrate BTCPay Server with our Next.js e-commerce application. **Requirements:** - Set up BTCPay Server integration using Greenfield API - Support both on-chain and Lightning Network payments - Real-time payment status via webhooks and SSE - QR code generation for payment addresses - Order status tracking and confirmation emails **Tech Stack:** - Next.js 16, TypeScript, Tailwind CSS - BTCPay Server (self-hosted) - PostgreSQL **Nice to have:** - Experience with LNURL and Lightning Address - Knowledge of BIP-21 URI scheme