The "email" field in the login screen should be type="email"

Summary: The HTML input type affects the keyboard that is offered on smartphone screens. We really want it to be type email, so that the @ is visible.

Pointed out by Aaron

The difficulty here is that it's actually email address or handle, and those same smartphones (Chrome, anyway) enforce the input format. So if it's set to "email", it won't accept handles, because they are missing the @. This seems to imply that we can't use the same field for either, which might imply a bit of redesign.

Note that whatever we do, it should apply to both the main login on the root screen, and the in-Querki login popup.