feat: AC button pill shape with 3D ledge press effect

- border-radius: 50px (pill shape matching animal-island-ui reference)
- box-shadow ledge: rgb(189,174,160) 0 5px in light, rgb(15,30,15) 0 5px in dark
- :active collapses ledge with translateY(5px) + box-shadow: none
- :hover lifts to 7px ledge
- fix: index.html fallback label Animal Crossing (was 动森)
- fix: remove redundant color on .card:hover

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

index.html

@@ -44,7 +44,7 @@
           </li>
           <li role="option" data-value="nord" aria-selected="false">Nord</li>
           <li role="option" data-value="animal-crossing" aria-selected="false">
-            动森
+            Animal Crossing
           </li>
         </ul>
       </label>