feat(ui): add marquee effect to video cards

- Add ellipsis truncation for titles and usernames
- Implement scroll-on-hover (desktop) and scroll-on-center (mobile)
- Fix mobile layout blowout using min-width: 0 on flex containers
- Add IntersectionObserver and ResizeObserver mocks for tests

css/tailwind.source.css

@@ -1051,6 +1051,7 @@
   }
 
   .card {
+    min-width: 0;
     --video-card-lift-translate-y: 0;
     --video-card-backdrop-opacity: 0;
     --video-card-backdrop-translate-y: var(--space-md-plus);