design: improve UI consistency and footer layout

- Update text sizing to text-base throughout for consistency
- Improve arrow icon visibility (gray-400 → gray-200 on hover)
- Reorganize tool badges: Open Source first, specialty second, Free third
- Update badge labels: Vert (Converter), Stirling (PDF), Units/Figlet (Open Source)
- Redesign footer: single-row layout with brand pill, centered copyright, GitHub link
- Update footer border: lighter gray-600, constrained to content width

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

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

components/Hero.tsx

@@ -93,7 +93,7 @@ export default function Hero() {
           animate={{ opacity: 1 }}
           transition={{ duration: 0.8, delay: 1 }}
         >
-          <span className="text-sm text-gray-500 group-hover:text-gray-400 transition-colors">Scroll to explore</span>
+          <span className="text-base text-gray-500 group-hover:text-gray-400 transition-colors">Scroll to explore</span>
           <motion.div
             className="w-6 h-10 border-2 border-gray-600 group-hover:border-purple-400 rounded-full p-1 transition-colors"
             animate={{ y: [0, 10, 0] }}