I need a developer who can jump into my existing codebase, troubleshoot the Google Firebase phone-number flow, and restore reliable OTP sign-in so users receive and verify codes without errors. Once the authentication bug is resolved, I also want Stripe payments and plans based on given disk space to users. This includes: Android, ios and web. Expect clean, well-commented code, brief hand-off notes, and a quick walkthrough showing both OTP login and a successful test payment working end-to-end.