fix: optimize animation and video previews

[phh235]

What does this PR do?

Optimizes animation and video preview performance across the landing page.

• Pauses marquee animations when outside the viewport.
• Defers preview video loading until needed.
• Pauses HeroReveal animation when hidden, out of view, or under reduced-motion preferences.
• Stops the automatic HeroReveal animation while the user is interacting with it.
• Adds proper cleanup for observers, animation frames, and event listeners.

Type of change

• Bug
• Component improvement

Checklist

• npx tsc --noEmit passes
• npm run lint passes
• npm run build passes
• Tested in Chrome (with the html-in-canvas flag, if relevant)
• Tested the WebGL overlay fallback (flag off / Safari / Firefox), if a component changed