feat(website): improve SeqSet citation metadata

[theosanderson-agent]

Summary

SeqSet citation author lists now retain up to ten names and use an ellipsis when additional contributors exist. This keeps citations readable without hiding normal-sized author lists.

The citation model now retains journal metadata from Crossref, persists it in the database, exposes it through the API, and displays it in public and administrative citation views. Manually curated citations can also supply a journal, including DOI metadata lookups.

Why

Citation views previously rendered every contributor, causing unusually long paper author lists to dominate the page. The backend also discarded Crossref journal metadata, leaving users without a key publication detail.
org.loculus.backend.service.crossref.CrossRefServiceTest --console=plain`

Preview evidence

🚀 Preview: https://agent-seqset-citation-aut.loculus.org

[claude]

This PR may be related to: #6918

[claude]

Claude finished @theosanderson's task in 2m 1s —— View job

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Code review

Todo list

• Gather context (read diff, changed files)
• Understand the request (code review)
• Review backend changes (Kotlin, DB migration)
• Review frontend changes (TS/React)
• Post inline comments for actionable issues
• Post final summary review

Summary

This is a clean, well-scoped change: adds a nullable journal column end-to-end (migration → API → DB service → frontend types/UI), and extracts a shared formatCitationContributors helper (with good spec coverage) to cap displayed author lists at 10 with an ellipsis, replacing duplicated inline formatting logic in AdminSeqSetCitationsTable.tsx and CitationTable.tsx.

Things I checked and confirmed are handled correctly:

• All three write paths in SeqSetCitationsDatabaseService.kt (CrossRef upsert, curated add, and both read/select mappings) consistently include the new journal column — no path silently drops it.
• The migration (V1.34__add_journal_to_seqset_citation_source.sql) is additive/nullable, matches schema.sql, and needs no backfill.
• CrossRefService.kt's journal_title extraction follows the same selectFirst/blank-check pattern already used for doi, year, title, etc., and is exercised by the updated CrossRefServiceTest.
• The journal display guard (!== undefined && !== null) is consistent with existing idioms elsewhere in the codebase (e.g. SeqSetItem.tsx), so no change needed there.

One minor point left as an inline comment on formatCitationContributors.ts: the ellipsis is shown even when only a single contributor would be hidden (11 → 10 shown + ...), which is likely intentional but worth a quick sanity check against the desired UX.

No security, performance, or test-coverage concerns found.