Anonymize selected categories of personally identifiable data on a candidate (for GDPR, CCPA, or other right-to-be-forgotten requests). The fields array selects which data groups to scrub — see the schema enum for the full set (e.g. full_name, email_addresses, phone_numbers, attachments, notes, scorecards_and_interviews). Anonymization is irreversible and runs asynchronously when the selected scope is large; the candidate's hiring activity remains intact for reporting.