feat: contacts and voucher assignment

lib/contacts.ts

@@ -0,0 +1,9 @@
+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;
+}