Add _VALID_EVENT_PREFIXES frozenset and validate event_type at all three
filter sites in audit.py (_build_filtered_query, _build_filtered_query
_with_handles, and the inline count query in list_audit_log). Invalid
values return HTTP 422. Also change like() pattern from prefix% to
prefix.% to enforce true prefix-match semantics.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
- Backend: add user_email to _build_filtered_query_with_handles (UserSubject join) and _audit_to_dict_with_handles; propagate through JSON viewer and CSV export including empty-result path
- Frontend: AuditLogTab adds Email column between User and Action Type; removes @ prefix from handle cell
- Test: update expected CSV header to include user_email
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>