Convert Flask-React Web App to Mobile APP using react-native and python-flask

I already run a production web application with a Python Flask API and a React front end. Now I want fully-featured mobile companions for both iOS and Android that talk to the same backend. For the first release, the app must faithfully reproduce three existing screens:

• Calendar page
• Registration page
• Billing page

The APIs that power these screens are live and documented, so the main work is designing a native-feeling UI, wiring up the endpoints, and packaging the builds for the App Store and Google Play. I’m open to the tech stack—React Native, Flutter, or another cross-platform approach—as long as it delivers smooth performance and maintains a single code base.

Please send a detailed project proposal outlining architecture choices, milestones, and how you will handle testing, store compliance, and ongoing maintenance. Source code, build instructions, and signed apps are expected at hand-off.