Comments can now have documents attached via multipart/form-data upload.
New endpoint GET /api/documents/comment/{id} to list a comment's files.
Document entity gains a comment relation with cascade remove.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Implement the sync orchestrator that delegates to tagged strategies via
AutowireIterator, and the HTTP controller exposing sync-preview and sync
endpoints with transaction wrapping and role-based access control.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>