test(admin): add unit tests for email blocklist controller and admin panel page

[vbudhram]

Because

• email-blocklist.controller.ts and PageEmailBlocklist/index.tsx had no unit tests. Sibling features (domain-blocklist, rate-limiting) do.

This pull request

• Adds email-blocklist.controller.spec.ts for list, add (valid input plus non-array, non-string, blank, > 768 chars, invalid regex syntax), remove (success, not-found, blank, non-string), and removeAll.
• Adds PageEmailBlocklist/index.test.tsx for render, loading, sort order, load error, button disable, submit + reload, whitespace guard, add-error alert, single delete (success + error), delete-all confirm/cancel, and CSV/TXT upload.
• Mirrors the test layout in PageDomainBlocklist and domain-blocklist.controller.spec.ts.

Issue that this pull request solves

Closes: https://mozilla-hub.atlassian.net/browse/FXA-13595

Checklist

Put an x in the boxes that apply

• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).
• I have manually reviewed all AI generated code.

[Copilot]

Pull request overview

Adds missing unit test coverage for the email regex blocklist feature in both the admin server (controller) and admin panel UI, aligning coverage with existing sibling blocklist/rate-limiting features.

Changes:

• Added NestJS unit tests for EmailBlocklistController covering list/add/remove/removeAll and validation edge cases.
• Added React Testing Library tests for PageEmailBlocklist covering loading/error states, add/delete flows, delete-all confirmation, and CSV/TXT upload behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/fxa-admin-server/src/rest/email-blocklist/email-blocklist.controller.spec.ts	Adds controller-level unit tests mirroring the existing domain blocklist controller test structure and validating email regex inputs.
packages/fxa-admin-panel/src/components/PageEmailBlocklist/index.test.tsx	Adds UI unit tests for the email regex blocklist page, mirroring PageDomainBlocklist patterns and covering add/remove/delete-all/file-upload flows.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.