Allow to add second device from main QR code scanner #6798

This issue is the result from a short discussion together with @r10s:

Right now, when scanning a QR code with the main QR code scanner, a dialog is shown "Please log out first":

Reference to the code:

Non-technical users won't understand which buttons they have to press to "log out".

Android and iOS, by contrast, simply allow scanning from the main scanner, with the reasoning that many users are happy to find a QR code scanner at all, and that the same-wifi requirement makes misuse hard.

If it is hard from a technical point of view to allow adding a second device from the main QR code scanner, then an alternative is to adapt the string to explain which buttons the user has to press to add a new profile.