polish: Priority 1 improvements - gradients, stats, metadata, footer

✨ Visual Enhancements:
- Unique gradients per tool (green-teal for Vert, orange-pink for Paint, indigo-purple for Pastel)
- Added new gradient utilities for better color differentiation

📊 Stats Section:
- New animated stats component showing "3 Tools, 100% Open Source, ∞ Privacy First"
- Glassmorphism cards with hover effects
- Icon badges for each stat

🔍 Enhanced Metadata:
- Comprehensive Open Graph tags for social sharing
- Twitter Card support
- Enhanced SEO with detailed keywords (vert, paint, pastel)
- Added SVG favicon with gradient toolbox icon
- Viewport meta tag and preconnect optimization

🔗 Improved Footer:
- 3-column responsive layout
- GitHub repository link with icon
- Quick links to all tools (Vert, Paint, Pastel)
- Tool count badge
- Updated tech stack mention (Next.js 16 & Tailwind CSS 4)

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

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

app/globals.css

@@ -68,3 +68,15 @@ body {
 @utility gradient-cyan-purple {
   background: linear-gradient(135deg, #2dd4bf 0%, #8b5cf6 100%);
 }
+
+@utility gradient-orange-pink {
+  background: linear-gradient(135deg, #f97316 0%, #ec4899 100%);
+}
+
+@utility gradient-green-teal {
+  background: linear-gradient(135deg, #10b981 0%, #06b6d4 100%);
+}
+
+@utility gradient-indigo-purple {
+  background: linear-gradient(135deg, #6366f1 0%, #a855f7 100%);
+}