SEO + responsive + structural improvements

- Add OG image, Twitter Card, canonical URL, JSON-LD structured data
- Add responsive CSS (768px + 480px breakpoints)
- Add print stylesheet
- Fix TOC: add missing sections (global-response, legal-response)
- Fix section numbering: "09½" → "10"
- Update footer: add "Last updated: 2026-03-14"
- Add sitemap.xml + robots.txt for search engine discovery
- Add .gitignore to exclude .bak files
- Create og-image.png (1200x630) for social sharing

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

og-image.svg

@@ -0,0 +1,12 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="1200" height="630" viewBox="0 0 1200 630">
+  <rect width="1200" height="630" fill="#0a0a0f"/>
+  <rect y="0" width="1200" height="4" fill="#ff4444"/>
+  <text x="600" y="180" text-anchor="middle" font-family="Arial,sans-serif" font-size="56" font-weight="bold" fill="#ff4444">SECURITY RESEARCH</text>
+  <text x="600" y="260" text-anchor="middle" font-family="Arial,sans-serif" font-size="42" fill="#e0e0e8">Alipay DeepLink Attack Surface</text>
+  <text x="600" y="320" text-anchor="middle" font-family="Arial,sans-serif" font-size="36" fill="#ff6b35">17 Vulnerabilities | CVSS 9.3 | 1B+ Users</text>
+  <text x="600" y="400" text-anchor="middle" font-family="Arial,sans-serif" font-size="28" fill="#9898a8">Whitelist Bypass — Remotely Exploitable by Anyone</text>
+  <text x="600" y="440" text-anchor="middle" font-family="Arial,sans-serif" font-size="28" fill="#9898a8">No Developer Permissions Required</text>
+  <rect x="380" y="480" width="440" height="50" rx="8" fill="#ff4444"/>
+  <text x="600" y="513" text-anchor="middle" font-family="Arial,sans-serif" font-size="24" font-weight="bold" fill="#fff">6 Global Investigations Active</text>
+  <text x="600" y="590" text-anchor="middle" font-family="Arial,sans-serif" font-size="20" fill="#4488ff">innora.ai/zfb — Innora AI Security Research</text>
+</svg>