Animations params in the API and MCP

Expose animation properties on layers through the API? Specifically things like:

- animation-delay (entry/exit timing per layer)
- animation-duration
- animation-name (e.g. fadeIn, slideInLeft)
- opacity keyframes

This would let us create fully animated video templates entirely via API without needing to touch the editor for the animation step. Right now we can set up all the layers, content, and styling programmatically, but have to jump into the editor to add the motion — which breaks the automation flow.

Even a simple set of properties per layer like entry_animation, entry_delay, exit_animation, exit_delay would be incredibly powerful.