SCIX-877 feat(metatags): gate Google Scholar tags by doctype

[thostetler]

Google Scholar-compatible meta tags were emitted on every abstract page regardless of doctype. Per SCIX-877 only a defined set of doctypes should expose them; non-scholarly doctypes (proposal, dataset, software, misc, pressrelease, catalog, talk, service, instrument) should not.

• Added a doctype whitelist and showsGoogleScholarTags predicate (scholarDoctypes.ts), matched case-insensitively
• Gated the Highwire (citation_), PRISM (prism.), and Dublin Core (dc.*) tag families behind the whitelist on the abstract page
• Left Schema.org JSON-LD, Open Graph, Twitter, canonical, and description tags emitted for all records
• Normalized doctype comparisons to lowercase (fixes prior title-case checks for proceedings, phdthesis, mastersthesis)
• Added unit tests covering whitelisted, removed, unlisted, missing, and case-insensitive doctypes

[codecov]

Codecov Report

❌ Patch coverage is 99.08257% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 61.2%. Comparing base (6a15785) to head (59c406c).

Files with missing lines	Patch %	Lines
src/components/Metatags/Metatags.tsx	98.6%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #883     +/-   ##
========================================
+ Coverage    61.2%   61.2%   +0.1%     
========================================
  Files         348     349      +1     
  Lines       41373   41430     +57     
  Branches     1826    1808     -18     
========================================
+ Hits        25297   25353     +56     
- Misses      16033   16034      +1     
  Partials       43      43             

Files with missing lines	Coverage Δ
src/components/Metatags/scholarDoctypes.ts	100.0% <100.0%> (ø)
src/components/Metatags/Metatags.tsx	95.8% <98.6%> (+0.5%)	⬆️

... and 1 file with indirect coverage changes

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