add Recovery Code support

[tanx]

The user should be able to write down a randomly generated Recovery Code that can be used in case the user has lost access to their 2FA methods (phone number, email, Google Authenticator) or forget their PIN.

This should be optional and available post onboarding e.g. in the wallet's settings.

This concept would be comparable to Apple's Recovery Key used to reset the Apple ID password or 2FA methods: https://support.apple.com/en-au/HT201487