CHW-5813 BulkActionRollback

bulk action executed partially before failing; previously-applied items have been rolled back so the request had no net effect

Default message: bulk action executed partially before failing; previously-applied items have been rolled back so the request had no net effect
HTTP status: 500 (server)

Problem. POST /api/actions/bulk rolled back. Cause. Per-item validation passed for every item, but a mid-execution failure forced a rollback of the items that had already executed; the bulk outcome is “nothing applied.” Fix. Read the response body for the underlying error from the failed item, resolve it, and retry. The atomic rollback guarantees no partial state to clean up. HTTP 500.