Get citation formats for a Scholar paper

Return MLA, APA, Chicago, Harvard, and Vancouver citation formats.

Currently returns HTTP 501. Google's cite-dialog endpoint (/scholar?q=info:<cluster>:scholar.google.com/&output=cite) returns HTTP 403 Forbidden for every unauthenticated client as of late 2026 — the dialog is only served to browsers that have an active Scholar JS session established via a prior /scholar page load. Working around that requires a stateful browser session which is not cost-effective for a single citation lookup.

Recommended workaround: call /v1/google/scholar/search for the paper and build a citation string client-side from the fields it already returns: title, authors (list), publication_info (which contains journal + year), and link. That's enough to assemble MLA / APA / Chicago / Harvard / Vancouver formats without making a second HTTP hop.

Tracked in scrape-badger/scrapebadger#135 follow-up work; this endpoint will be re-enabled when we add a browser-session-backed fetch path.