refactor: standardize mailer configuration by introducing a config module and renaming related environment variables.

app/api/contact/route.ts

@@ -56,19 +56,20 @@ export async function POST(req: Request) {
 
     // 2. Email sending
     try {
+      const { config } = await import("@/lib/config");
       const transporter = nodemailer.createTransport({
-        host: process.env.SMTP_HOST,
-        port: parseInt(process.env.SMTP_PORT || "587"),
-        secure: process.env.SMTP_SECURE === "true",
+        host: config.mail.host,
+        port: config.mail.port,
+        secure: config.mail.port === 465,
         auth: {
-          user: process.env.SMTP_USER,
-          pass: process.env.SMTP_PASS,
+          user: config.mail.user,
+          pass: config.mail.pass,
         },
       });
 
       await transporter.sendMail({
-        from: process.env.SMTP_FROM,
-        to: process.env.CONTACT_RECIPIENT || "info@mb-grid-solutions.com",
+        from: config.mail.from,
+        to: config.mail.recipients.join(",") || "info@mb-grid-solutions.com",
         replyTo: email,
         subject: `Kontaktanfrage von ${name}`,
         text: `