Dashboard: warn when the account email address is bouncing

[leonardost]

Part of DOTOBRD-370

Proposed Changes

• Show a non-dismissible warning at the top of the sites list when mail to the signed-in user's account email address is hard-bouncing, with one CTA to change that address and one to add a recovery email.
• Eligibility comes from a new read-only user_email_bouncing boolean on /me/settings, prefetched in the sitesRoute loader so the banner is settled before first paint.

This is the frontend half. The wpcom /me/settings change is separate. Either half can land first: with the field absent the notice stays hidden, so this is safe to merge before the API change deploys.

Why are these changes being made?

A user whose account email no longer accepts mail cannot recover their account — both the password reset and the login link need a working inbox, and the only email-free route asks for a username that is usually autogenerated and unknown to the user. 7.9% of lockout tickets come from a bouncing account email.

We cannot email these users to tell them; that is the problem itself. Many of them can still sign in, so the dashboard is the only channel we have to reach them.

The field is derived from the current account email, so it flips to false on its own once the user completes an email change. There is no dismissal state and nothing to clean up.

Testing Instructions

1. Sign in to the dashboard and open /sites.
2. With a normal account, nothing changes.
3. To see the notice before the API half deploys, seed the cache in the browser console or stub the response so /me/settings returns user_email_bouncing: true. The warning appears above the site list, showing the account email address, with no dismiss button.
4. Confirm the primary CTA goes to /me/account and the secondary to /me/security/account-recovery.
5. Confirm it is the only on-load banner shown, since it outranks the other arbiter candidates.

Automated coverage: yarn test-client client/dashboard/app/account-email-bouncing-notice client/dashboard/sites/test/index.test.tsx

Note on the shared test helper: render() in client/dashboard/test-utils.tsx gains an optional config option. The default app config used by tests has supports.me: false, so a test could not otherwise exercise a notice gated on it. The option is additive with the previous config as its default, so no existing test changes behavior.

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?
• For UI changes, have you tested the affected components in dark mode?
• Have you tested accessibility for your changes? Ensure the feature remains usable with various user agents (e.g., browsers), interfaces (e.g., keyboard navigation), and assistive technologies (e.g., screen readers) (PCYsg-S3g-p2).
• 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)?

🤖 Generated with Claude Code

https://claude.ai/code/session_01TRxJcPXk1VER7bjwek5AZF

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