Redesign DemoSection with additional layout, content adjustments, and new demos

- Added User Dashboard demo with `UserCircle` icon and "NEW" badge.
- Introduced "View Complete Demo Tour" CTA linking to the Demo Tour page.
- Adjusted grid layout to support 4 columns for better spacing: `md:grid-cols-2 lg:grid-cols-4`.
- Enhanced Demo credentials modal with richer content outlining user and admin account capabilities.
- Adjusted navigation links: renamed "Components" to "Design System" and added Demo Tour link.
- Updated Demo Tour with leisurely paths, feature checklists, and new demo categories (user and admin flows).

frontend/src/components/home/Header.tsx

@@ -19,7 +19,8 @@ export function Header({ onOpenDemoModal }: HeaderProps) {
   const [mobileMenuOpen, setMobileMenuOpen] = useState(false);
 
   const navLinks = [
-    { href: '/dev', label: 'Components' },
+    { href: '/', label: 'Home' },
+    { href: '/dev', label: 'Design System' },
     { href: '/admin', label: 'Admin Demo' },
   ];