Display recovery key of a vault

### Summary

As a user I want to be able to display the [recovery key](
https://docs.cryptomator.org/en/latest/desktop/password-and-recovery-key/#show-recovery-key) of a vault while creating a new one as well as later during use.

### Motivation

In disaster scenarios, it can be useful to have a recovery key to get back to the data in the vault, for example, if the master key file is broken and no backup exists. Before that, you had to have stored the recovery key somewhere safe, for which it is necessary to display it like in the desktop app.