feat: Add Light node for scene lighting

[jb0gie]

Summary

Add a new Light node supporting three light types (directional, point, spot) for scene lighting in Hyperfy worlds.

Changes

• New file: src/core/nodes/Light.js - Light node implementation (305 lines)
• Modified: src/core/nodes/index.js - Export light node (+1 line)

Light Types

• directional: Infinite light with direction (e.g., sun)
• point: Omnidirectional light from a point (e.g., bulb)
• spot: Cone-shaped light with angle and penumbra (e.g., flashlight)

Properties

Property	Type	Default	Description
type	string	'point'	Light type
color	string	'#ffffff'	Light color (hex)
intensity	number	1	Light brightness
distance	number	100	Max distance (point/spot)
decay	number	2	Falloff rate (point/spot)
angle	number	Math.PI/3	Cone angle (spot)
penumbra	number	0	Edge softness (spot)
castShadow	boolean	false	Cast shadows

Usage Example

const light = app.create('light', {
  type: 'point',
  color: '#ff00ff',
  intensity: 2,
  distance: 50
})
light.position.set(0, 2, 0)
app.add(light)

Testing

• Create directional light
• Create point light
• Create spot light
• Modify properties at runtime
• Verify shadows work when castShadow=true