Fix remaining ESLint errors: replace img with Next.js Image, fix useEffect dependency, correct nodemailer method

src/app/api/send-scheduled-emails/route.ts

@@ -244,7 +244,7 @@ export async function GET() {
     const smtpConfig = configDoc.data();
 
     // Create transporter
-    const transporter = nodemailer.createTransporter({
+    const transporter = nodemailer.createTransport({
       host: smtpConfig.host,
       port: smtpConfig.port,
       secure: smtpConfig.secure,