Integrate Solvapay SDK

Implement Solvapay SDK integration with stack-specific guides and shared references.

Quick Start

1. Detect stack from package.json.
2. Read the matching stack guide:
   • nextjs/guide.md
   • react/guide.md
   • express/guide.md
   • mcp-server/guide.md
3. Use reference.md for shared API patterns.
4. Use webhooks.md when webhook handling is required.

Stack Detection Rules