feat: add HN launch readiness features

Launch checklist implementation:
- Add Privacy Policy page (/privacy) with GDPR compliance
- Add Terms of Service page (/terms)
- Add custom 404 and error pages with helpful navigation
- Add FAQ page (/faq) covering common questions
- Add SEO meta tags with OpenGraph/Twitter cards
- Add JSON-LD structured data (Organization, WebSite, SoftwareApplication)
- Add sitemap.ts and robots.ts for search engines
- Add security headers (HSTS, CSP, X-Frame-Options) in vercel.json
- Add security.txt at /.well-known/security.txt
- Add API rate limiting (100 req/min default, 20 req/min strict)
- Add empty states in tool search for better UX
- Update AppHeader with FAQ link
- Update AppFooter with Privacy/Terms links
- Update biome.json to allow dangerouslySetInnerHTML for JSON-LD in page files

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

packages/config/biome.json

@@ -66,6 +66,16 @@
           }
         }
       }
+    },
+    {
+      "include": ["**/layout.tsx", "**/page.tsx"],
+      "linter": {
+        "rules": {
+          "security": {
+            "noDangerouslySetInnerHtml": "off"
+          }
+        }
+      }
     }
   ]
 }