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/showcase/mobile/.expo/README.md

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+> Why do I have a folder named ".expo" in my project?
+
+The ".expo" folder is created when an Expo project is started using "expo start" command.
+
+> What do the files contain?
+
+- "devices.json": contains information about devices that have recently opened this project. This is used to populate the "Development sessions" list in your development builds.
+- "settings.json": contains the server configuration that is used to serve the application manifest.
+
+> Should I commit the ".expo" folder?
+
+No, you should not share the ".expo" folder. It does not contain any information that is relevant for other developers working on the project, it is specific to your machine.
+Upon project creation, the ".expo" folder is already added to your ".gitignore" file.

packages/showcase/mobile/.expo/devices.json

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+{
+  "devices": []
+}