Fix: return the post-move modified time from document updates

Editing a document in a way that renames its file returned a response carrying the modified time from before the move. The deferred file move runs after the response is built and bumps modified, so the stored value was newer than the one the client received. The frontend then saw a newer server modified time and showed a spurious "document was updated" prompt whose reload discarded local edits.

DocumentViewSet.update now flushes pending file moves right after saving and before reading the document back, so the response reflects the final filename and modified time.

src/documents/views.py

@@ -128,6 +128,7 @@ from documents.data_models import ConsumableDocument
 from documents.data_models import DocumentMetadataOverrides
 from documents.data_models import DocumentSource
 from documents.file_handling import format_filename
+from documents.file_moves import flush_pending_file_moves
 from documents.filters import CorrespondentFilterSet
 from documents.filters import CustomFieldFilterSet
 from documents.filters import DocumentFilterSet
@@ -1291,6 +1292,8 @@ class DocumentViewSet(
         )
         serializer.is_valid(raise_exception=True)
         self.perform_update(serializer)
+        # The response must reflect the post-move filename and modified time
+        flush_pending_file_moves()
 
         if content_updated and content_doc.id != root_doc.id:
             content_doc.content = (