export function validateContact(c: { name: string; email: string | null; telegramChatId: string | null }): string[] {
  const errs: string[] = [];
  if (!c.name?.trim()) errs.push("name");
  const email = c.email?.trim() ?? "";
  const chat = c.telegramChatId?.trim() ?? "";
  if (!email && !chat) errs.push("kanal");
  if (email && !/^[^@\s]+@[^@\s]+\.[^@\s]+$/.test(email)) errs.push("email");
  return errs;
}