Better preview UI

Synchronization between FX and JS Players

• Added JavaScript bridge functions (playAnimation(), pauseAnimation(), stopAnimation(), seekToFrame())
• Synchronized all playback controls so both players start/stop/pause/seek together
• Added frame slider synchronization for manual seeking
• Backgrounds can now be set and tested

Fixed Positioning/Layout Differences

• Corrected TrimPath offset calculation for animation
• Fixed angle normalization to properly handle wrapping