feat: migrates Course Optimizer from Redux to React Query.

[navinkarkera]

Description

This removes the old Redux slice, selectors, and thunks. It also improves scan status polling and stale-result handling.

This affects Course Authors and Instructors who can edit course content. There is no intended UI change.

Supporting information

• Switch from Redux to React Query + Context #2540

Testing instructions

1. Open a course in Studio with course-content edit access.
2. Open Course Optimizer; add /optimizer to url from outline.
3. Add a html xblock with some broken links
4. Start a link check and confirm the scan status updates.
5. Review the scan results.
6. Rerun the scan and confirm new results replace old results.
7. Update all broken links and update an individual link.
8. Refresh the page during and after an operation.
9. Confirm errors are shown if an API request fails.

Best Practices Checklist

• Any new files are using TypeScript (.ts, .tsx).
• Avoid propTypes and defaultProps in any new or modified code.
• Tests use the helpers in src/testUtils.tsx.
• No new fields were added to Redux.
• React Query is used for REST API data.
• New i18n messages have translator descriptions.
• Avoid using ../ in import paths.

[openedx-webhooks]

Thanks for the pull request, @navinkarkera!

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[codecov]

Codecov Report

❌ Patch coverage is 96.21849% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.93%. Comparing base (91d76aa) to head (dc573ba).

Files with missing lines	Patch %	Lines
src/optimizer-page/scan-results/ScanResults.tsx	90.72%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3204      +/-   ##
==========================================
- Coverage   95.93%   95.93%   -0.01%     
==========================================
  Files        1397     1395       -2     
  Lines       33622    33506     -116     
  Branches     7700     7696       -4     
==========================================
- Hits        32256    32144     -112     
+ Misses       1323     1319       -4     
  Partials       43       43              

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[bradenmacdonald]

I'm not super familiar with the course optimizer code. When this is ready, could you please check the PRs or git blame to see if one of the main authors may want to review it? If they decline and/or in any case, me or Chris can give the necessary ✅ though.