Fix: Delete chunk images on document parser config change. (#12262)

### What problem does this PR solve?

Modifying a document’s parser config previously left behind obsolete
chunk images. If the dataset isn’t manually deleted, these images
accumulate and waste storage. This PR fixes the issue by automatically
removing associated images when the parser config changes.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

api/apps/document_app.py

@@ -746,6 +746,7 @@ async def change_parser():
             tenant_id = DocumentService.get_tenant_id(req["doc_id"])
             if not tenant_id:
                 return get_data_error_result(message="Tenant not found!")
+            DocumentService.delete_chunk_images(doc, tenant_id)
             if settings.docStoreConn.index_exist(search.index_name(tenant_id), doc.kb_id):
                 settings.docStoreConn.delete({"doc_id": doc.id}, search.index_name(tenant_id), doc.kb_id)
         return None