QR Code Scanner Issues

As noted here:

First, attempting to follow the flow via the in-app Scan Login Code button never succeeds—the camera never acknowledged the QR. I think we should create a separate issue to address the broken flow on a Samsung Galaxy S20 running Android 13.

Second, I note a few visual issues that may or may not relate to these proposed changes:

• The cancel button on the first screen is invisible, but selectable via a screen reader.
• The large text leading (space between lines) on the first screen feels too tight.
• We might consider announcing the result of the asynchronous login work (i.e., have TalkBack announce whether it succeeds or fails), currently the user has no idea whether something occurred without waiting an indeterminate amount of time and then manually navigating the newly populated screen text.

Start by reading the flow described in PR #21330 and reproducing the in-app Scan Login Code path on a Samsung Galaxy S20 running Android 13. Check QR recognition, the first screen's cancel button and text spacing, and whether TalkBack announces asynchronous login success or failure.