fix: download button in playground + de-emphasize rate limits

- Fix download button: exclude #demoDownload from smooth scroll handler
  that was calling preventDefault() on blob: URLs after PDF generation
- Replace '5,000 PDFs per month' with 'High-volume PDF generation' in pricing
- Update schema.org structured data to remove specific limits

public/app.js

@@ -302,8 +302,9 @@ document.addEventListener('DOMContentLoaded', function() {
     el.addEventListener('click', function(e) { e.preventDefault(); openRecover(); });
   });
 
-  // Smooth scroll for hash links
+  // Smooth scroll for hash links (exclude download link)
   document.querySelectorAll('a[href^="#"]').forEach(function(a) {
+    if (a.id === 'demoDownload') return;
     a.addEventListener('click', function(e) {
       var target = this.getAttribute('href');
       if (target === '#') return;