added mail service

components/auth/BackButton.tsx

@@ -0,0 +1,18 @@
+'use client'
+
+import { Button } from '@/components/ui/button'
+import Link from 'next/link'
+
+type Props = {
+  href: string
+  label: string
+}
+
+export const BackButton = ({ href, label }: Props) => {
+  return (
+    <Button variant="link" size="sm"
+            className="font-normal w-full" asChild>
+      <Link href={href}>{label}</Link>
+    </Button>
+  )
+}