Block ability to max transaction size after scanning QR code

[janklosowski]

When you pay with the app by scanning a QR code, you cannot edit the amount manually. However, you can click the "Total available amount," and send all funds by accident. After the change, there is no way to go back to the original amount (except scanning the QR code again). Also, it's easy to miss since the amount is dimmed, so the change is not visually striking.

It seems like something that shouldn't be available at all in this context, but at least the change should be reversible.