SCIX-942 fix(author-affiliation): download Excel export as binary

[thostetler]

The author-affiliation Excel export downloaded a file Excel refused to open, because axios decoded the binary response as UTF-8 text before it reached the browser.

• Excel exports are now requested as arraybuffer; useDownloadFile accepts BlobPart instead of only strings, so binary and string downloads both work.
• jsdom's XHR corrupts binary the same way axios's old text path did, so tests pin axios' fetch adapter to cover the fetch logic; the real browser download was verified by hand against the live API.

[github-actions]

Bundle size

Shared by all pages: 627.7 kB (+0.0 kB) ⚪

No route changed by more than 1 kB. ✅

_{First load = polyfills + shared _app chunks + route chunks, gzipped.}

[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.2%. Comparing base (a815fbe) to head (4477602).

Files with missing lines	Patch %	Lines
src/lib/useDownloadFile.ts	70.0%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #951     +/-   ##
========================================
- Coverage    55.2%   55.2%   -0.0%     
========================================
  Files         378     379      +1     
  Lines       11618   11643     +25     
  Branches     2554    2554             
========================================
+ Hits         6406    6416     +10     
- Misses       4574    4586     +12     
- Partials      638     641      +3     

Files with missing lines	Coverage Δ
src/api/author-affiliation/author-affiliation.ts	52.7% <100.0%> (ø)
src/components/AuthorAffiliations/models.ts	100.0% <100.0%> (ø)
src/lib/useDownloadFile.ts	80.4% <70.0%> (-1.0%)	⬇️

... and 7 files with indirect coverage changes

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