Fix layer planes example orientation

[Kkkakania]

References and relevant issues

Closes #245

Description

Set the layer planes example camera orientation explicitly to the pre-0.6 axis direction. napari 0.6 changed the default depth axis from away to towards, which mirrored the example relative to its intended camera path. Keeping the orientation local to this example restores the original animation without changing global viewer defaults.

Verification

• Executed examples/layer_planes.py with napari 0.8.0 using the native macOS Qt backend
• Rendered all 121 frames and produced the complete MP4 successfully
• uvx pre-commit run --files examples/layer_planes.py
• python -m compileall -q examples/layer_planes.py

A full Sphinx Gallery run reached example execution locally, but macOS Qt offscreen OpenGL terminated in an unrelated earlier 3D example. The target example itself completed under the native backend.