Improve showcase pages: drawers, modals, badges, and Vite caching fix

- DTDrawer: storefront-matching dual-element bevel border, slide-in/out
  animations from correct edge, 99vh height, bold 2em header, box shadow
- DTModal: interactive demos on Bevels page with all 5 mode variants
- Badges: solid color fill with contrasting text (black on dark, white on light)
  instead of transparent fill with colored text
- Animations: add dt-slide-right and dt-slide-left keyframes for drawers
- Bevels page: remove trash "Button Bevels", add interactive modal/drawer
  demos, fix media frame to use real images with proper bevel styling
- Advanced Cards: remove redundant media frame sections, rename "Menu Items"
  to "Buttons", remove DTButton/dt-btn references
- Forms page: rename "Menu Items" to "Buttons"
- Vite config: exclude design system packages from optimizeDeps pre-bundling
  and watch dist directories to prevent stale CSS during development

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

packages/web/src/components/animations.css

@@ -21,6 +21,16 @@
   to   { transform: translateY(0); }
 }
 
+@keyframes dt-slide-right {
+  from { transform: translateX(100%); }
+  to   { transform: translateX(0); }
+}
+
+@keyframes dt-slide-left {
+  from { transform: translateX(-100%); }
+  to   { transform: translateX(0); }
+}
+
 /* ============================================================================
    Interactive Animations
    ============================================================================ */