Update Woo rebrand auth signin and magic link pages

[ilyasfoo]

Related to #96945, #96947, #97056

Proposed Changes

• Update Woo branding for sign in, sign in (while logged in), email magic link, and post-email magic link
• Remove user name from Continue as user name button in sign in (while logged in) page
• Add mobile responsiveness for some copies
• Add mixins into SCSS

Testing Instructions

• In your development.json, set woocommerce/rebrand-2-0 to true
• Run yarn start

Sign in page

• In an incognito window, go to this URL
• Observe the changes match with Figma tp2u3Nk9arcpeNMZcylNG4-fi-271_8254

Email magic link

• Continuing from above instructions, click on Email me a login link
• Observe the changes match with screenshot (No Figma available)
• Try entering an email and observe the button UI changes, matching with tp2u3Nk9arcpeNMZcylNG4-fi-112_6447

Post-email magic link

• Continuing from above instructions, enter an email and click on Send link
• Observe the changes match with Figma tp2u3Nk9arcpeNMZcylNG4-fi-271_8309
• Try entering an email and observe the button UI changes, matching with tp2u3Nk9arcpeNMZcylNG4-fi-112_6447

Sign in page (while signed in)

• Using a window where WordPress.com is logged in, go to this URL
• tp2u3Nk9arcpeNMZcylNG4-fi-271_8267

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
  • For UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:commit-671c3fcb8ab5366b97abc956e9468383de5b24b6

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:commit-671c3fcb8ab5366b97abc956e9468383de5b24b6&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:commit-671c3fcb8ab5366b97abc956e9468383de5b24b6&env=a8c-for-agencies

[ilyasfoo]

Changes meant outside of feature flag

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

App Entrypoints (~26 bytes added 📈 [gzipped])

name         parsed_size           gzip_size
entry-login        -37 B  (-0.0%)      +26 B  (+0.0%)

Common code that is always downloaded and parsed every time the app is loaded, no matter which route is used.

Sections (~25 bytes added 📈 [gzipped])

name             parsed_size           gzip_size
accept-invite          -68 B  (-0.0%)       +0 B
jetpack-connect        -37 B  (-0.0%)      +25 B  (+0.0%)

Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Async-loaded Components (~25 bytes added 📈 [gzipped])

name                          parsed_size           gzip_size
async-load-signup-steps-user        -68 B  (-0.0%)       +0 B
async-load-design-blocks            -37 B  (-0.0%)      +25 B  (+0.0%)

React components that are loaded lazily, when a certain part of UI is displayed for the first time.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[moon0326]

LGTM and tested well 👍 🚀

[psealock]

Code looks good 🚢