Exposes a CommentService method that maps a collection of commentIds to their annotationIds via commentRepository.findAllById. Unknown comments and comments with null annotationId are omitted. Used by the dashboard activity feed enrichment to supply the deep-link annotationId without growing the audit SQL query. Refs #300. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>