feat: remove projects section and availability badge

- Drop projects section, nav link and data (ProjectCard removed in c5ff89f)
- Swap hero "View projects" button for a GitHub link
- Remove "Open to new opportunities" badge

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

components/Header.js

@@ -6,7 +6,6 @@ import Icon from './Icon';
 const links = [
   { href: '/#about', label: 'About' },
   { href: '/#stack', label: 'Stack' },
-  { href: '/#projects', label: 'Projects' },
 ];
 
 export default function Header() {