Senior React Developer — Codebase Refactoring (React + Capacitor + Supabase)

We have a fully functional React + Capacitor fitness app currently in active beta for the Android platform with iOS to follow. The app is performing well and has a solid feature set. The entire frontend currently lives in a single 37,000-line App.js file that needs to be refactored into a proper feature module structure by a disciplined, experienced developer. This is a refactoring engagement, not a feature development engagement. No new features. No logic changes. Functionality must remain identical before and after every step. If you are looking for greenfield work, this is not the right fit. If you have done this kind of careful, methodical work on a large production codebase and take pride in leaving code cleaner than you found it, this could be a good fit. Nice to have: Familiarity with AWS Lambda and API Gateway. We have a planned migration from Vercel serverless to AWS at scale and want someone who can help architect that transition.