Android App Development

I need a native Android mobile application built from scratch and taken all the way to a Play Store–ready release. Core features for the first version are: • Secure user authentication / sign-in • Push notifications (Firebase Cloud Messaging is fine) • In-app purchases using Google Play Billing You are free to use Android Studio with Kotlin or Java—whichever you work fastest in—so long as the code is clean, well-commented, and easy for another developer to pick up later. Deliverables – Compiled APK/AAB ready for internal testing and final production upload – Complete, organized source code in a Git repository – Brief setup README covering build steps, key libraries, and how to configure the notification and purchase services The project will be considered done once I can install the release build, create an account, receive a test push notification, and successfully execute a test purchase in the sandbox environment.