[native] avoid showing SIWE backup message screen for non-primary devices

Summary:
ENG-9905.

This a fix for ENG-9917.

Depends on D13967

Test Plan:
This is the final diff so testing this end-to-end.
I was scanning the QR code using my physical iOS device, secondary was the web and other iOS physical devices. I was testing this on both passwords and wallet users.
Things I checked:

• Secondary logged in
• Secondary received backup data (but ignored this for now)
• On primary, the camera was dismissed and Secondary was added to the list
• Tunnel broker connection (auth) created
• Device list updates are sent

Things I didn't test (not sure if I should):

• keyserver auth
• scanning on Android (I don't have access to this device when creating this stack, I can do it later in the week)

Reviewers: bartek, tomek, varun

Reviewed By: bartek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13968