Warn about passwordless accounts

https://redmine.teklia.com/issues/7318

Requires backend#1757 (closed) and #1417 (closed)

When a user is logged in but does not have a password set, App.vue should show a warning notification, just like the existing warning for unverified emails. It should be styled as is-warning to scream louder than for unverified emails, because users really need to notice that they will never be able to log in again if they log out, or at least not without doing a time-consuming password reset.

The banner should include a link to the user profile page to invite users to set their password.

Note that both the user profile page and the PartialUpdateUser endpoint require a user to be verified, so this banner cannot be displayed when the user is logged in but does not have a verified email, or it will be even more confusing.