feat(phase-4): Task 1 — audit log backfill in auth.py and documents.py (D-13)
- Add write_audit_log import to auth.py and documents.py
- auth.py: login success (auth.login), login failure (auth.login_failed, no PII),
logout (auth.logout), logout-all (auth.sign_out_all), change-password
(auth.password_changed), TOTP enable (auth.totp_enrolled), TOTP disable
(auth.totp_revoked), backup code used (auth.backup_code_used)
- documents.py: upload confirm (document.uploaded, size+backend only),
document delete (document.deleted, size only — no filename/extracted_text)
- Add request: Request param to change_password, disable_totp, confirm_upload, delete_document