The Firebase project for my Android app is already live and linked; the last missing piece is phone-number OTP sign-in. I want the Firebase Mobile-OTP flow embedded directly into the current login screen, re-using the existing UI and design language—no extra screens. My total budget for this task is ₹5,000, and I’d like to wrap it up quickly without cutting corners on user experience or security. Deliverables • Code that hooks Firebase Authentication (phone/SMS) into the present login activity or fragment, including resend, timeout, error, and auto-retrieval handling. • Any required updates to gradle files, SHA-1 fingerprints, or Firebase console settings clearly documented. • A short README or screencast showing the end-to-end flow running on an emulator or device. Acceptance criteria – The app builds cleanly in Android Studio and signs users in with their phone number using Firebase’s standard verification flow. – OTP auto-verification works where supported; manual entry works everywhere else. – Incorrect or expired codes are handled gracefully with user-friendly messages. – No regressions to existing email/password or guest login paths. Tech in play: Firebase Authentication, Android Studio, Flutter, Google Play services. Hand over a working pull request or zipped module, and we’re done.