Cross-Platform User Registration App

I need a single mobile code-base that runs smoothly on both iOS and Android. The first milestone is simple yet critical: secure user registration. When someone installs the app they should be able to create an account with an email (or phone), confirm it through a verification link or code, and land on a clean welcome screen.

The framework is up to you—Flutter, React Native, Kotlin Multiplatform, anything that compiles to native binaries and is easy for me to maintain later. Please write clean, well-commented code and follow Apple’s Human Interface and Google’s Material guidelines so the builds are ready for TestFlight and Internal Testing without extra polishing.

Deliverables
• Production-ready iOS (.ipa) and Android (.aab) builds
• Full source code with README covering environment setup, build commands, and where to plug in store keys
• Basic UI aligned with modern mobile standards
• Short hand-over session to walk me through publishing and future feature extension

Acceptance criteria
1. A new user can sign up, verify, sign in, and sign out without errors.
2. All network traffic is encrypted (HTTPS).
3. The same codebase produces both platform binaries with identical functionality.

That’s the entire scope for now; later I may add payments and push notifications once this foundation is live.