Our auth-related pages that include forms (such as the login page,

registration, Forget Password, and others) try to achieve a clean visual

style where the fields are centered and the labels are to the left of

the fields. This was done using some fixed widths and some margin

offsets, and didn't always translate well when additional content was

injected onto a page.
This change redoes the styling to get rid of the hacks and instead

utilize flexbox and CSS grid to get our balanced look without

hard-coding much of anything, and without needing much in the way of

style overrides specific to new content on the page. This makes these

pages easier to maintain and extend, which is important for some

in-progress work.
These also achieve a better mobile look, with fields providing more

space for entry on smaller screens without compromising layout or

introducing unwanted padding.
In the process, a regression in error styling has been fixed (it was

lacking a color hint) and buttons have been updated to use Ink.
The styling all applies to the somewhat legacy auth-* CSS classes, to

maintain compatibility. Rebuilding these for a CSS Component scheme is

out of scope, and best suited for a future version of Ink.

Tested the login page with/without SSO and a captcha.
Tested the registration page.
Tested the SSO login flow and account linking.
Tested the Forget Password flow.
Tested with in-progress code building upon these forms.
All tests were conducted with desktop and mobile modes at various

widths and wrap levels.