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

Setup: two runs of the same course

1. Create (or pick) a course run in Studio, e.g. course-v1:Org+CS100+T1 (the old run). Add a few units with pages so there are real internal destinations (outline page, a section page, the course page itself).
2. Using the same course (same org + course number), create a new run, e.g. course-v1:Org+CS100+T2. Open the new run once so its pages render.
3. In the new run, open any HTML component and paste in at least three internal URLs copied from the old run - copy them directly from the browser address bar of old-run pages (course page, outline, or a unit page). Do not retype them; exact old-run URLs are what the link check detects.
4. Also add one intentionally broken external link (e.g. https://example.com/this-page-does-not-exist-12345) in an HTML component, to cover the broken-links path.
5. Publish the changes in the new run (unpublished changes are not scanned).

Exercise Course Optimizer in the new run

6. Open the new run in Studio and go to Course Optimizer (add /optimizer to the outline URL). Confirm the tool loads with no prior scan data.
7. Start a link check and confirm the scan status updates while it runs (progress/pending state is visible, no stuck spinner).
8. Review the scan results. Confirm both categories appear:
   • Links to previous course run: your pasted old-run URLs, each tagged with the component/location.
   • Broken links: the fake external URL.
9. Rerun the scan and confirm the new results fully replace the old results (no duplicated or stale rows).
10. Click one link's individual Update action and confirm only that link is updated while at least two previous-run links remain.
11. Click Update all. Confirm:
    • The button shows its pending state and then succeeds.
    • All remaining results are marked updated, and their old-run URLs are replaced with the new run key.
12. Open all three updated components in the new run (or use the course outline / LMS preview) and confirm every link now resolves to a page in the new run - clicking them stays within course-v1:Org+CS100+T2.
13. Refresh the page during an in-flight operation (scan or update) and after it completes; confirm the UI recovers correctly (status re-fetches, results persist, no phantom "in progress" state).
14. Force an API failure (e.g. stop the backend or block the optimizer endpoint in devtools) and start a scan or click Update all; confirm an error alert is shown and the UI returns to a usable state.

Expected overall

• No UI regressions vs. pre-migration behavior; this PR changes state management only.
• Scan polling, rerun, Update all, individual update, refresh recovery, and error handling all work against a course with links to a previous run.

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!

This repository is currently maintained by @bradenmacdonald.

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[codecov]

Codecov Report

❌ Patch coverage is 98.03922% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.04%. Comparing base (91d76aa) to head (5314098).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/optimizer-page/scan-results/ScanResults.tsx	95.57%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3204      +/-   ##
==========================================
+ Coverage   95.93%   96.04%   +0.10%     
==========================================
  Files        1397     1395       -2     
  Lines       33622    33581      -41     
  Branches     7700     7988     +288     
==========================================
- Hits        32256    32253       -3     
+ Misses       1323     1287      -36     
+ Partials       43       41       -2     

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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.

[navinkarkera]

@dcoa @jesperhodge @Faraz32123 Can you please review this PR? I am tagging you based of the commit history of the files in the PR, let me know if don't have time or cannot review it for some reason.