feat(responsive,seo): implement responsive design and SEO optimizations

Phase 4: Responsive Design Optimizations
- Increase touch target sizes to min 44px for mobile
- Add touch-manipulation for better touch handling
- Optimize button and input sizes for mobile devices
- Implement responsive font sizing (16px -> 17px -> 18px)

Phase 5: SEO Optimizations
- Enhance metadata with comprehensive Open Graph tags
- Add Twitter Card metadata with images
- Implement Google Search Console verification
- Add structured data (Organization, Website schemas)
- Improve keywords and descriptions

Files modified:
- src/components/ui/button.tsx: Touch-friendly sizes
- src/components/ui/input.tsx: Mobile-optimized inputs
- src/app/globals.css: Responsive font sizing
- src/app/layout.tsx: Enhanced metadata and structured data
- src/components/seo/structured-data.tsx: New structured data components

Impact:
- Better mobile user experience
- Improved search engine visibility
- Enhanced social media sharing
- WCAG 2.1 touch target compliance
- Better SEO performance

src/app/globals.css

@@ -112,6 +112,18 @@
     text-rendering: optimizeLegibility;
   }
   
+  @media (min-width: 640px) {
+    html {
+      font-size: 17px;
+    }
+  }
+  
+  @media (min-width: 1024px) {
+    html {
+      font-size: 18px;
+    }
+  }
+  
   body {
     background-color: var(--color-bg-primary);
     color: var(--color-text-primary);