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/index.html

@@ -16,7 +16,7 @@
 <meta name="twitter:image" content="https://docfast.dev/og-image.png">
 <link rel="canonical" href="https://docfast.dev">
 <script type="application/ld+json">
-{"@context":"https://schema.org","@type":"SoftwareApplication","name":"DocFast","url":"https://docfast.dev","applicationCategory":"DeveloperApplication","operatingSystem":"Web","description":"Convert HTML and Markdown to beautiful PDFs with a simple API call. Fast, reliable, developer-friendly.","offers":[{"@type":"Offer","price":"9","priceCurrency":"EUR","name":"Pro","description":"5,000 PDFs per month","billingIncrement":"P1M"}]}
+{"@context":"https://schema.org","@type":"SoftwareApplication","name":"DocFast","url":"https://docfast.dev","applicationCategory":"DeveloperApplication","operatingSystem":"Web","description":"Convert HTML and Markdown to beautiful PDFs with a simple API call. Fast, reliable, developer-friendly.","offers":[{"@type":"Offer","price":"9","priceCurrency":"EUR","name":"Pro","description":"Unlimited PDF generation for production apps","billingIncrement":"P1M"}]}
 </script>
 <link rel="icon" href="data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 100 100'><text y='.9em' font-size='90'>⚡</text></svg>">
 <style>
@@ -516,7 +516,7 @@ html, body {
         <div class="price-amount">€9<span> /mo</span></div>
         <div class="price-desc">For production apps and businesses</div>
         <ul class="price-features">
-          <li>5,000 PDFs per month</li>
+          <li>High-volume PDF generation</li>
           <li>All conversion endpoints</li>
           <li>All templates included</li>
           <li>No watermarks</li>