Extract consent, audit log, cookie category, and consent stats endpoints
from legal_document_routes into LegalDocumentConsentService. The route
file is now a thin handler layer delegating to LegalDocumentService and
LegalDocumentConsentService with translate_domain_errors(). Legacy
helpers (_doc_to_response, _version_to_response, _transition,
_log_approval) and schemas are re-exported for existing tests. Two
transition tests updated to expect domain errors instead of HTTPException.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>