Fix XR menu panel scaling for distant model placement

[samaneh-kazemi]

Issue:
When models are placed far away in AR, the XR menu panel maintains a fixed physical size, making it appear too small and difficult to interact with from the user's perspective.

Solution

• Implemented distance-based scaling for the XR menu panel that automatically adjusts the panel size based on the distance to the camera:
• Base scale: 1.0x at minimum distance (0.5m)
• Maximum scale: ~3.85x at maximum distance (10m)
• Scaling factor: 0.3x per meter of distance
• Uniform scaling: Both panel background and buttons scale together