Request Erasure

Schedule data-subject erasure (GDPR art. 17 / CCPA deletion). Admin-only: Bearer keys are full-power within the tenant; operators need ``role=ADMIN``. Refuses with 409 while any flow is still open (PENDING / AWAITING_INPUT / PROCESSING / NEEDS_REVIEW) — reviewers must disposition open cases before the evidence is destroyed. The applicant disappears from list/get immediately (``erased_at``); the arq ``erase_applicant`` job then deletes the S3 documents and the applicant's DB rows. ``audit_log`` rows are deliberately retained (legal-obligation basis, GDPR art. 17(3)(b)) — they carry hashes and ids, not PII, and the job writes a hashes-only ``applicant.erased`` tombstone as the durable record that erasure happened.