Feature request: Keyboard shortcuts to toggle visibility of all layers (image, labeling, segmentation)

[AxolotlPrime]

When annotating images in Labkit, I frequently need to toggle the
visibility of different layers (image, labeling, segmentation overlay)
to compare them against each other. Currently this requires a mouse
click on the respective eye icon every single time, which interrupts
the annotation workflow significantly.

I would like to suggest keyboard shortcuts for toggling the visibility
of all three layer types:

• Image layer: e.g. I
• Labeling layer: e.g. Space (note: N already cycles through labels,
  so a visibility toggle via Space would be a natural complement)
• Segmentation overlay: e.g. V (consistent with napari, where
  toggle_selected_visibility is mapped to V by default)

This would greatly speed up quality control and annotation workflows,
especially when working with large tiled images where constantly
switching between views is necessary.