Upload Campaign Resume

Campaign candidate provides their resume on the lobby (before Start) — a FILE or PASTED TEXT. Replaces the interview's synthetic resume_text with the real thing (so the brain personalizes the opener) and stores the parsed structure on the candidate so it shows in the recruiter's dashboard. Both writes matter: without the second, has_resume stays false and the recruiter never sees it.

Paste is supported because this endpoint absorbed the /screen page's resume step — that page took pasted text, and dropping the option would have shut out candidates who don't have a file to hand.

Public + token-scoped, and GATED to campaign screenings only (metadata.source == 'campaign_screen') — a normal interview's token can never reach this write path.