feat(06-02): branded signing request email + mailer utilities

- Add SigningRequestEmail.tsx React Email component (navy/gold brand colors, CTA button)
- Add signing-mailer.tsx with sendSigningRequestEmail() and sendAgentNotificationEmail()
- Uses CONTACT_SMTP_* env vars (same SMTP provider as contact form)
- Sender: "Teressa Copeland" <teressa@teressacopelandhomes.com>

teressa-copeland-homes/src/lib/signing/signing-mailer.tsx

@@ -0,0 +1,67 @@
+import { render } from '@react-email/render';
+import nodemailer from 'nodemailer';
+import { SigningRequestEmail } from '@/emails/SigningRequestEmail';
+import React from 'react';
+
+function createTransporter() {
+  return nodemailer.createTransport({
+    host: process.env.CONTACT_SMTP_HOST!,
+    port: Number(process.env.CONTACT_SMTP_PORT ?? 587),
+    secure: false,
+    auth: {
+      user: process.env.CONTACT_EMAIL_USER!,
+      pass: process.env.CONTACT_EMAIL_PASS!,
+    },
+  });
+}
+
+export async function sendSigningRequestEmail(opts: {
+  to: string;
+  clientName?: string;
+  documentName: string;
+  signingUrl: string;
+  expiresAt: Date;
+}): Promise<void> {
+  const expiryDate = opts.expiresAt.toLocaleDateString('en-US', {
+    month: 'long',
+    day: 'numeric',
+    year: 'numeric',
+  });
+  const html = await render(
+    React.createElement(SigningRequestEmail, {
+      documentName: opts.documentName,
+      signingUrl: opts.signingUrl,
+      expiryDate,
+      clientName: opts.clientName,
+    })
+  );
+  const transporter = createTransporter();
+  await transporter.sendMail({
+    from: '"Teressa Copeland" <teressa@teressacopelandhomes.com>',
+    to: opts.to,
+    subject: `Please sign: ${opts.documentName}`,
+    html,
+  });
+}
+
+export async function sendAgentNotificationEmail(opts: {
+  clientName: string;
+  documentName: string;
+  signedAt: Date;
+}): Promise<void> {
+  const formattedTime = opts.signedAt.toLocaleString('en-US', {
+    month: 'long',
+    day: 'numeric',
+    year: 'numeric',
+    hour: 'numeric',
+    minute: '2-digit',
+    timeZoneName: 'short',
+  });
+  const transporter = createTransporter();
+  await transporter.sendMail({
+    from: '"Teressa Copeland Homes" <teressa@teressacopelandhomes.com>',
+    to: 'teressa@teressacopelandhomes.com',
+    subject: `Signed: ${opts.documentName}`,
+    text: `${opts.clientName} has signed "${opts.documentName}" on ${formattedTime}.`,
+  });
+}