How I added Solana Pay USDC to a SaaS app — a real implementation, not a tutorial

Most Solana Pay tutorials are synthetic. Here's the actual code running in production on transpiler.us, a developer tools platform I built solo. Why Solana Pay instead of Stripe-only I already had Stripe. But Stripe doesn't work everywhere, and USDC settling instantly with near-zero fees is genuinely better for global users. It wasn't about looking good — it was the right technical choice. The implementation The flow: user clicks "Pay with USDC" → backend generates a reference keypair → frontend