fix(VTKjs): Fix type imports from VTK.js

Fixes type imports from '@kitware/vtk.js/types'.

Resolves observed error when developing against a local VTK.js
development branch:

```sh
 ERROR  Error: The following dependencies are imported but could not be resolved:                             16:46:24

  @kitware/vtk.js/types (imported by C:/repos/VolView/src/components/tools/polygon/PolygonWidget2D.vue?id=0)

Are they installed?
    at file:///C:/repos/VolView/node_modules/vite/dist/node/chunks/dep-df561101.js:45705:23
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async file:///C:/repos/VolView/node_modules/vite/dist/node/chunks/dep-df561101.js:45114:38
```

src/components/tools/BoundingRectangle.vue

@@ -6,7 +6,7 @@ import { worldToSVG } from '@/src/utils/vtk-helpers';
 import { nonNullable } from '@/src/utils/index';
 import vtkLPSView2DProxy from '@/src/vtk/LPSView2DProxy';
 import vtkBoundingBox from '@kitware/vtk.js/Common/DataModel/BoundingBox';
-import { Bounds, Vector3 } from '@kitware/vtk.js/types';
+import type { Bounds, Vector3 } from '@kitware/vtk.js/types';
 import { onVTKEvent } from '@/src/composables/onVTKEvent';
 
 const props = defineProps<{

src/components/tools/polygon/PolygonWidget2D.vue

@@ -25,7 +25,7 @@ import vtkWidgetFactory, {
   vtkPolygonViewWidget as WidgetView,
 } from '@/src/vtk/PolygonWidget';
 import { Maybe } from '@/src/types';
-import { Vector3 } from '@kitware/vtk.js/types';
+import type { Vector3 } from '@kitware/vtk.js/types';
 import { useViewStore } from '@/src/store/views';
 import {
   onViewProxyMounted,