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/public/robots.txt

@@ -1,5 +1,12 @@
 # robots.txt - SmoothSchedule
-# Deny all robots while in development
+# Currently blocking all crawlers - site not yet live
 
 User-agent: *
 Disallow: /
+
+# When ready to go live, replace above with:
+# User-agent: *
+# Allow: /
+# Disallow: /api/
+# Disallow: /admin/
+# Sitemap: https://smoothschedule.com/sitemap.xml