export function validateCredentials(username, password) {
  const u = (username || '').trim()
  const p = password || ''
  if (!u) return { ok: false, code: 'EMPTY_USERNAME', message: '请输入用户名 / 工号' }
  if (!p) return { ok: false, code: 'EMPTY_PASSWORD', message: '请输入密码' }
  return { ok: true }
}