feat: add transformPerspective prop and card flip demo

[janicduplessis]

Summary

Adds a transformPerspective prop to control the 3D camera distance for rotateX/rotateY animations, and a card flip demo showcasing it.

Previously, perspective was hardcoded to 850 on iOS and Android, with no way to customize it and no perspective on web at all. The default is now 1280, matching React Native's own default, and the value is configurable per-view.

Platform-specific implementation:

• iOS: Perspective (m34) is included in the composed CATransform3D model transform. Transform animations use individual Core Animation key-paths (transform.rotation.y, transform.scale.x, etc.) instead of full-matrix interpolation to avoid the "fold" artifact on large rotations. For interrupted animations, "from" values are read from the presentation layer; for completed animations, old prop values are used as fallback since CA can't reliably decompose rotation angles from a matrix that also contains m34.
• Android: Camera distance uses RN's actual normalization formula (density² × perspective × √5). backfaceVisibility: 'hidden' now works correctly — setBackfaceVisibilityDependantOpacity() is called on first mount and during rotation animations.
• Web: perspective() CSS transform function is added when the animate prop declares rotateX/rotateY. Perspective and rotation are always included in the transform (even at 0°) so CSS transitions interpolate correctly between states.

iOS caveat: On iOS, the parent view must not be flattened by Fabric for perspective to render correctly. The parent needs collapsable={false} or a style that prevents flattening (e.g. transform, zIndex). This is because Fabric can remove "empty" parent views from the native hierarchy, which breaks the 3D rendering context.

Test plan

• Run the Card Flip demo on iOS, Android, and web
• Verify 3D perspective is visible during the flip animation
• Verify backfaceVisibility: 'hidden' correctly hides the back face on all platforms
• Test rapid tapping (animation interruption) — should smoothly redirect mid-animation
• Test with different transformPerspective values (e.g. 400 for dramatic, 2000 for subtle)
• On iOS, verify the parent container has collapsable={false} for correct rendering