fix(seo): Block crawlers and add sitemap

- Set robots meta tag to noindex, nofollow (site not live)
- Update robots.txt with instructions for going live
- Add sitemap.xml with all marketing pages

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

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

frontend/index.html

@@ -23,7 +23,7 @@
     <meta name="twitter:image" content="https://smoothschedule.com/og-image.png" />
 
     <!-- Additional SEO -->
-    <meta name="robots" content="index, follow" />
+    <meta name="robots" content="noindex, nofollow" />
     <meta name="author" content="Smooth Schedule Inc." />
     <link rel="canonical" href="https://smoothschedule.com" />
     <link href="https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&display=swap" rel="stylesheet">