Add storefront component migration: cards, badges, progress bars, animations, and React wrapper package

Major feature migration from dt-shopify-storefront into the design system:

- Card system: per-card color modes (normal/emphasis/warning/success/other),
  progress bars, full-bleed card body (card-body-flush), image bevel clip-paths,
  and visible structural borders at bevel corners
- Badge system: dt-card-badge with position-aware offsets for cards vs media frames
- Media frames: dt-bevel-media with inner surface fill, image clipping, and
  "MISSING MEDIA" placeholder for empty containers
- Interactive bevel buttons: dt-btn with hover/selected states and pulse animation
- Menu items: dt-menu-item with active states and level indentation
- Animations: scale-in, fade-in, slide-up, pulse, ping, spin keyframes
- Feature legend: CSS grid for product feature icons with state colors
- Scrollbar styling for DT brand
- New @dangerousthings/react package wrapping web CSS components
- New @dangerousthings/tailwind-preset package
- New @dangerousthings/hex-background package
- Desktop showcase rewritten in React with Tailwind CSS
- Mobile showcase updated with new screens (animations, filters, advanced cards)
- Tokens: added mode color tokens, RGB variants, and selected-state tokens

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/react/src/components/DTMenu.tsx

@@ -0,0 +1,108 @@
+/**
+ * DTMenu — Hierarchical menu with beveled items.
+ *
+ * CSS reference: forms-dt.css .dt-menu-item, .active, .selected
+ */
+
+import { useState, useCallback, type ReactNode, type CSSProperties } from 'react';
+import type { DTVariant } from '@dangerousthings/tokens';
+import { cx } from '../utils/cx';
+import { getVariantClass } from '../utils/variantClasses';
+
+export interface DTMenuItem {
+  id: string;
+  title: string;
+  icon?: ReactNode;
+  items?: DTMenuItem[];
+  isActive?: boolean;
+  isSelected?: boolean;
+}
+
+interface DTMenuProps {
+  items: DTMenuItem[];
+  /** Color variant @default 'normal' */
+  variant?: DTVariant;
+  onItemClick?: (id: string) => void;
+  className?: string;
+  style?: CSSProperties;
+}
+
+export function DTMenu({
+  items,
+  variant = 'normal',
+  onItemClick,
+  className,
+  style,
+}: DTMenuProps) {
+  return (
+    <div
+      className={cx(getVariantClass(variant), className)}
+      style={{ display: 'flex', flexDirection: 'column', gap: '4px', ...style }}>
+      {items.map(item => (
+        <MenuItem
+          key={item.id}
+          item={item}
+          level={0}
+          onItemClick={onItemClick}
+        />
+      ))}
+    </div>
+  );
+}
+
+function MenuItem({
+  item,
+  level,
+  onItemClick,
+}: {
+  item: DTMenuItem;
+  level: number;
+  onItemClick?: (id: string) => void;
+}) {
+  const [expanded, setExpanded] = useState(false);
+  const hasChildren = item.items && item.items.length > 0;
+
+  const handleClick = useCallback(() => {
+    if (hasChildren) {
+      setExpanded(prev => !prev);
+    }
+    onItemClick?.(item.id);
+  }, [hasChildren, item.id, onItemClick]);
+
+  return (
+    <>
+      <button
+        className={cx(
+          'dt-menu-item',
+          item.isActive && 'active',
+          item.isSelected && 'selected',
+        )}
+        style={{ '--dt-menu-level': level } as CSSProperties}
+        onClick={handleClick}
+        aria-expanded={hasChildren ? expanded : undefined}
+        type="button">
+        <span style={{ display: 'flex', alignItems: 'center', gap: '8px' }}>
+          {item.icon}
+          {item.title}
+        </span>
+        {hasChildren && (
+          <span
+            className="dt-accordion-chevron"
+            style={{
+              transition: 'transform 250ms ease-in-out',
+              transform: expanded ? 'rotate(180deg)' : undefined,
+            }}
+          />
+        )}
+      </button>
+      {hasChildren && expanded && item.items!.map(child => (
+        <MenuItem
+          key={child.id}
+          item={child}
+          level={level + 1}
+          onItemClick={onItemClick}
+        />
+      ))}
+    </>
+  );
+}