feat: migrar emails de Resend a Nodemailer + Gmail SMTP

Reemplaza Resend por nodemailer con Gmail SMTP. El to: ahora usa
el email real del cliente en lugar del hardcodeado de sandbox.
Variables de entorno: GMAIL_USER y GMAIL_APP_PASSWORD.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/magic-link.ts

@@ -1,21 +1,28 @@
 import { prisma } from "./prisma";
-import { Resend } from "resend";
+import nodemailer from "nodemailer";
 import crypto from "crypto";
 
-const resend = new Resend(process.env.RESEND_API_KEY);
+const transporter = nodemailer.createTransport({
+  host: "smtp.gmail.com",
+  port: 587,
+  secure: false,
+  auth: {
+    user: process.env.GMAIL_USER,
+    pass: process.env.GMAIL_APP_PASSWORD,
+  },
+});
 
 export async function enviarMagicLink(email: string): Promise<{ ok: boolean; error?: string }> {
   const cliente = await prisma.cliente.findUnique({ where: { email } });
   if (!cliente) return { ok: false, error: "Email no registrado" };
 
-  // Invalidar tokens anteriores no usados
   await prisma.magicToken.updateMany({
     where: { clienteId: cliente.id, usado: false },
     data: { usado: true },
   });
 
   const token = crypto.randomBytes(32).toString("hex");
-  const expiresAt = new Date(Date.now() + 15 * 60 * 1000); // 15 minutos
+  const expiresAt = new Date(Date.now() + 15 * 60 * 1000);
 
   await prisma.magicToken.create({
     data: { clienteId: cliente.id, token, expiresAt },
@@ -23,9 +30,9 @@ export async function enviarMagicLink(email: string): Promise<{ ok: boolean; err
 
   const link = `${process.env.MAGIC_LINK_BASE_URL}/cliente/auth?token=${token}`;
 
-  await resend.emails.send({
-    from: "Taller <onboarding@resend.dev>",
-    to: "jpbeldomenico@gmail.com",
+  await transporter.sendMail({
+    from: `"Taller" <${process.env.GMAIL_USER}>`,
+    to: email,
     subject: "Tu link de acceso al taller",
     html: `
       <h2>Hola ${cliente.nombre}!</h2>