feat(web): Next.js 15 shell — design tokens, landing, auth pages

apps/web/components/ui/button.tsx

@@ -0,0 +1,45 @@
+import * as React from 'react';
+import { cn } from '@/lib/cn';
+
+type Variant = 'primary' | 'secondary' | 'ghost' | 'danger';
+type Size = 'sm' | 'md' | 'lg';
+
+const variants: Record<Variant, string> = {
+  primary:
+    'bg-[--color-accent] text-[--color-accent-fg] hover:bg-[#5557e8] active:bg-[#4f51d8] border border-transparent',
+  secondary:
+    'bg-[--color-bg-elevated] text-[--color-fg] hover:bg-[--color-bg-subtle] border border-[--color-border]',
+  ghost:
+    'bg-transparent text-[--color-fg-muted] hover:text-[--color-fg] hover:bg-[--color-bg-subtle] border border-transparent',
+  danger:
+    'bg-transparent text-[--color-danger] hover:bg-[rgba(239,68,68,0.08)] border border-[--color-border]',
+};
+
+const sizes: Record<Size, string> = {
+  sm: 'h-7 px-2.5 text-xs gap-1.5',
+  md: 'h-8 px-3 text-[13px] gap-2',
+  lg: 'h-10 px-4 text-sm gap-2',
+};
+
+export interface ButtonProps extends React.ButtonHTMLAttributes<HTMLButtonElement> {
+  variant?: Variant;
+  size?: Size;
+}
+
+export const Button = React.forwardRef<HTMLButtonElement, ButtonProps>(function Button(
+  { className, variant = 'secondary', size = 'md', ...props },
+  ref,
+) {
+  return (
+    <button
+      ref={ref}
+      className={cn(
+        'inline-flex items-center justify-center rounded-md font-medium tracking-tight transition-colors duration-200 ease-out disabled:opacity-50 disabled:pointer-events-none select-none',
+        variants[variant],
+        sizes[size],
+        className,
+      )}
+      {...props}
+    />
+  );
+});