refactor(ui): unify low-level controls and expand design system

src/components/layout/Header.tsx

@@ -1,6 +1,6 @@
 import Link from 'next/link';
 import { auth } from '@/lib/auth';
-import { RocketIcon } from '@/components/ui';
+import { RocketIcon, getButtonClassName } from '@/components/ui';
 import { ThemeToggle } from './ThemeToggle';
 import { UserMenu } from './UserMenu';
 import { WorkshopsDropdown } from './WorkshopsDropdown';
@@ -36,7 +36,7 @@ export async function Header() {
           ) : (
             <Link
               href="/login"
-              className="flex h-9 items-center rounded-lg bg-primary px-4 text-sm font-medium text-primary-foreground transition-colors hover:bg-primary-hover"
+              className={getButtonClassName({ size: 'sm' })}
             >
               Connexion
             </Link>