[feat] Add horse movement speed control UI

[hasjack]

Overview

Implement a UI control for adjusting horse movement speed with different gaits.

Proposed Gaits

• Walk: 1/16 horse length per frame (~450px/sec)
• Trot: 1/8 horse length per frame (~900px/sec)
• Canter: 1/4 horse length per frame (~1800px/sec)

Implementation Details

1. Add speed state to useMovement hook
2. Create UI component for speed control
3. Add visual feedback for current gait
4. Consider keyboard shortcuts for speed changes

Considerations

• Ensure smooth transitions between speeds
• Add appropriate animations for each gait
• Consider sound effects for different gaits
• Maintain path constraints at higher speeds

[hasjack]

Updated Gait Speeds

After testing and calibration, here are the proper speeds for each gait:

• Walk: 1/64 horse length per frame (~112px/sec)
• Trot: 1/32 horse length per frame (~225px/sec) - Current default
• Canter: 1/16 horse length per frame (~450px/sec)
• Gallop: 1/8 horse length per frame (~900px/sec)

These speeds feel more natural and match typical horse movement patterns. The current default trot provides a comfortable pace for exploration while maintaining the feeling of controlled movement.