Update lab desk objects, textures, and positions

[davetcoleman]

Summary

• Move desk forward (Y: 1.1 → 0.9) to be closer to the robot
• Add granite texture overlay on desk surface
• Make stirrer movable by adding freejoint
• Reposition test tube stand from (-0.7, 0.85) to (0.3, 0.85) and align parallel to robot rail
• Move desk bottles forward to more accessible positions
• Update desk material specular/shininess properties

Dependencies

• Used by moveit_pro_example_ws#512

Test plan

• Launch lab_sim and verify desk is closer to the robot
• Verify granite overlay renders on desk surface
• Verify stirrer is movable in simulation
• Verify test tube stand is behind the custom rack
• Verify bottles are in accessible positions on the desk

[rlpratt12]

This is for https://github.com/PickNikRobotics/moveit_pro/issues/17169 (priority for sprint 133)

[davetcoleman]

Can we just merge this now? Won't affect the current example_ws since its tagged to a specific commit