feat(mail): add smtp email delivery

lib/mail/types.ts

@@ -0,0 +1,13 @@
+import type { ContactInquiry, RepairInquiry, SmtpSettings } from "@/lib/admin/types";
+
+export type PublicSmtpSettings = Omit<SmtpSettings, "password"> & {
+  hasPassword: boolean;
+};
+
+export type MailSendResult = {
+  ok: boolean;
+  error?: string;
+};
+
+export type ContactMailInput = ContactInquiry;
+export type RepairMailInput = RepairInquiry;