fix: QA audit bugs BUG-051/052/056/057/059/062/063/064/065/066/068

- BUG-056: Fix sitemap namespace sitemapns.org -> sitemaps.org
- BUG-062: Extend <main> to wrap all page content (hero+features+pricing+EU section)
- BUG-064: Add sr-only <label> elements to all modal form inputs (signup, recovery, change-email)
- BUG-051/052: Remove duplicate X-Content-Type-Options headers from nginx (let helmet handle)
- BUG-057: Fix JSON-LD and pricing card: Pro plan is 2,500 PDFs/month not 5,000
- BUG-059: Add meta description, canonical URL, og: tags to /docs page
- BUG-063: Change eu-hosting h3 to h2 (correct heading hierarchy)
- BUG-065/066: Add aria-modal=true, role=dialog to modals; aria-label=Close to close buttons
- BUG-068: Add hash-based modal open for #change-email on page load
- Add .sr-only CSS utility class to base and index styles

public/status.html

@@ -44,6 +44,8 @@ footer .container { display: flex; justify-content: space-between; align-items:
   footer .container { flex-direction: column; text-align: center; }
   .nav-links { gap: 16px; }
 }
+
+.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }
 </style>
 <style>
 .status-hero { text-align: center; padding: 48px 0 32px; }