Add email confirmation note to subscription page

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: jmitchel3

src/pages/confirm-subscription.astro

@@ -10,6 +10,9 @@ import BaseLayout from '@/layouts/BaseLayout.astro';
         <p class="text-lg text-[var(--color-text-muted)]">
           Thanks for subscribing. I'll send you an email when I publish something new.
         </p>
+        <p class="mt-4 text-[var(--color-text-muted)]">
+          Look for an email from <strong>justin@justinmitchel.com</strong> to confirm your subscription.
+        </p>
         <p class="mt-8">
           <a href="/" class="text-[var(--color-accent)] hover:underline">Back to home</a>
         </p>