BiasManan2010/zeppay ? reverse-engineered prompt

Build me a Flutter app called Zep Pay that makes UPI payments feel much simpler, especially on Android.

The main flow should be, scan a UPI QR, enter the amount, confirm with biometrics, then let the app hand off to the phone call flow for *99# or 123PAY so the user only has to enter their UPI PIN. I also want the everyday money tools around it, like sending requests, splitting bills with friends, viewing payment history, and setting up autopay.

It should work offline first, keep data locally, and be ready to swap in a backend later without changing the whole UI. For login, use SMS OTP with a simple dev fallback code if the OTP service is not set up yet. On Android, include the needed camera and phone permissions and make the payment handoff feel smooth. On iPhone, just use a web style handoff to open UPI apps. If you need to, look up the latest Flutter and platform docs online before wiring up the phone and biometric parts.