[Bug]: Text selection, copy&paste impossible in mobile Add Transaction Amount input field

### What happened?

The amount field in the mobile Add Transaction sheet is not a regular HTML input field. Despite that it should mostly act like one. Currently, it does not, including the lack of possibility of copy&paste and text selection.

### How can we reproduce the issue?

1. Open the Add Transaction sheet on mobile.
2. Try selecting text by tapping/long tapping inside the amount input field.
3. It either does nothing or shows/hides the virtual keyboard.

### Where are you hosting Actual?

Other

### What browsers are you seeing the problem on?

Safari

### Operating System

Mobile Device