I already have a live Firebase project connected to my Flutter application on both Android and iOS. Email/Password sign-in is working, but Phone Authentication still needs to be wired up and I’m unsure whether the phone number should be linked to the existing email accounts or kept separate. What I need from you is a clean, production-ready implementation of Firebase Phone Authentication using the firebase_auth package (Dart), complete with OTP verification, error handling, and platform-specific configuration in Android Studio and Xcode. Please walk me through the pros and cons of linking phone numbers to the current Email/Password users so I can choose the right flow, then implement that choice in code. The work is finished for me when: • Both platforms can send and verify the SMS code successfully. • The chosen account-linking strategy is fully implemented and explained. • I receive concise setup notes so I can replicate the steps in future builds. If this sounds straightforward to you and you’re comfortable with Flutter, Firebase Console, Gradle, and Xcode entitlements, let’s get started.