When a document (PPTX, DOCX, XLSX, ODP, ODT, ODS) is attached, extracted slide images were left orphaned after removing the parent text entry. This adds a sourceDocumentId field to AttachedFile that links all entries from the same document extraction, and cascades removal of all entries in the group when any one is removed. Fixes #2426 Co-authored-by: chiamsun <chiamsun@users.noreply.github.com>