Passkeys: Activity indication/UI freezing

Registering or authorizing with passkeys requires multiple hits to the server, which can take some time. We should make sure there is some sort of activity indication while that is happening.

Also while we are at it right now it is possible to simply continue hitting the register or auth button which will then try to auth or register multiple times. We should either lock the ui during these processes or we should at least disable the buttons while processing.

Locate the passkey registration and authorization entry points in the iOS app and trace the server requests they start. Check how the register and authorize buttons handle in-progress work. Done means users see activity feedback while processing and cannot trigger duplicate registration or authorization attempts.

Written by the indexing model from the issue text.