I need a developer who can wire a payment-processing API into both my mobile application (iOS and Android) and its companion web app. The core task is to enable smooth, secure checkout flows—card capture, tokenisation, refunds, and webhook handling—so users experience the same friction-free payment journey no matter which platform they use. You will be given: • Existing front-end codebases for React Native and React (both already live in staging). • Backend endpoints ready to accept the payment tokens. • Sandbox credentials for the payment gateway I’m using. What I expect back: • Fully working payment flows on mobile and web, tested in sandbox and promoted to production. • Clear, commented code plus a short integration guide so my in-house team can maintain it. • Error handling, logging, and confirmation screens that match our current UI patterns. • Final walk-through and hand-over session. I’m open to Stripe, PayPal or a similarly robust gateway—choose whichever you’re most comfortable with, provided PCI-compliant best practices are followed. If you have recent experience shipping payment APIs on both app and web stacks, I’d love to see it.