Add SMTP mail utility, admin settings page, and API routes for SMTP configuration and test email

shop/utils/mail.ts

@@ -0,0 +1,44 @@
+// utils/mail.ts – simple wrapper around nodemailer
+import nodemailer from 'nodemailer';
+
+// Load SMTP configuration from environment variables
+const smtpConfig = {
+  host: process.env.SMTP_HOST,
+  port: Number(process.env.SMTP_PORT),
+  secure: process.env.SMTP_SECURE === 'true' || process.env.SMTP_SECURE === '1', // true for 465, false for other ports
+  auth: {
+    user: process.env.SMTP_USER,
+    pass: process.env.SMTP_PASS,
+  },
+};
+
+// Create a reusable transporter. If any required var is missing, nodemailer will throw on send.
+const transporter = nodemailer.createTransport(smtpConfig);
+
+/**
+ * Send an email.
+ * @param to Recipient address
+ * @param subject Subject line
+ * @param text Plain‑text body
+ * @param html Optional HTML body
+ */
+export async function sendMail({
+  to,
+  subject,
+  text,
+  html,
+}: {
+  to: string;
+  subject: string;
+  text: string;
+  html?: string;
+}) {
+  const info = await transporter.sendMail({
+    from: smtpConfig.auth.user,
+    to,
+    subject,
+    text,
+    html,
+  });
+  return info;
+}