chore(deps): upgrade @kitware/vtk.js to 35.15.1

Bumps @kitware/vtk.js from ^32.12.1 to ^35.15.1.

Per vtk.js BREAKING_CHANGES (33 -> 34), several volume mapper setters
were moved from the mapper onto the volume property. Adjust callers to
invoke the new property-based setters:

- src/utils/volumeProperties.ts: route the relevant set* calls through
  the volume's property instead of the mapper.
- src/components/vtk/VtkBaseVolumeRepresentation.vue: same migration for
  the representation component's mapper/property interactions.

Author: PaulHax