export function getApiErrorMessage(err: unknown): string | null {
  if (!err || typeof err !== 'object') return null
  const anyErr = err as Record<string, unknown>
  const response = anyErr.response as Record<string, unknown> | undefined
  const data = response?.data as Record<string, unknown> | undefined
  const msg = data?.error
  return typeof msg === 'string' ? msg : null
}