Cross platform private/pub key pair backup and restoration flow

[thebentern]

Upon want-config flow connection, we will receive the security config section containing the two keys.

1. One option is to prompt the user to backup this security configuration in a secure store on the phone. Perhaps this prompt can be triggered based on checking if we have stored this already for the current node (by nodenum), if not, then we prompt the user
2. Subsequently to the backup flow, we can check if the keys are different (a flash wipe or catastrophic filesystem loss occurred), if they are different, we can prompt the user to restore the original keys from the securely stored backup or to update the backup with the new keys.
3. Another alternative to this more automated flow would be a manual backup and restoration within the configuration section of the app.