fix: evaluate copyright year in email footer template (refs #221)

Add missing $ prefix to template literal expression so the year
renders as "2026" instead of literal "{new Date().getFullYear()}".

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

backend/src/features/notifications/domain/email-layout/base-layout.ts

@@ -68,7 +68,7 @@ export function renderEmailLayout(content: string): string {
                       <a href="https://motovaultpro.com/settings" style="${EMAIL_STYLES.footerLink}" target="_blank">Manage Email Preferences</a>
                     </p>
                     <p style="${EMAIL_STYLES.copyright}">
-                      &copy; {new Date().getFullYear()} MotoVaultPro. All rights reserved.
+                      &copy; ${new Date().getFullYear()} MotoVaultPro. All rights reserved.
                     </p>
                   </td>
                 </tr>