3dgs & ply support (#7602)

## Summary

integrated sparkjs https://sparkjs.dev/, built by [world labs
](https://www.worldlabs.ai/) to support 3dgs.

- Add 3D Gaussian Splatting (3DGS) support using @sparkjsdev/spark
library
- Add PLY file format support with multiple rendering engines
- Support new file formats: `.ply`, `.spz`, `.splat`, `.ksplat`
- Add PLY Engine setting with three options: `threejs` (mesh), `fastply`
(optimized ASCII point clouds), `sparkjs` (3DGS)
- Add `FastPLYLoader` for 4-5x faster ASCII PLY parsing
- Add `original(Advanced)` material mode for point cloud rendering with
THREE.Points

3dgs generated by https://marble.worldlabs.ai/

test ply file from:
1. made by https://github.com/PozzettiAndrea/ComfyUI-DepthAnythingV3
2. threejs offically repo

## Screenshots


https://github.com/user-attachments/assets/44e64d3e-b58d-4341-9a70-a9aa64801220



https://github.com/user-attachments/assets/76b0dfba-0c12-4f64-91cb-bfc5d672294d



https://github.com/user-attachments/assets/2a8bfe81-1fb2-44c4-8787-dff325369c61



https://github.com/user-attachments/assets/e4beecee-d7a2-40c9-97f7-79b09c60312d

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7602-3dgs-ply-support-2cd6d73d3650814098fcea86cfaf747d)
by [Unito](https://www.unito.io)

src/components/load3d/controls/viewer/ViewerModelControls.vue

@@ -10,7 +10,7 @@
       />
     </div>
 
-    <div>
+    <div v-if="!hideMaterialMode">
       <label>{{ $t('load3d.materialMode') }}</label>
       <Select
         v-model="materialMode"
@@ -32,6 +32,11 @@ import type {
 } from '@/extensions/core/load3d/interfaces'
 import { t } from '@/i18n'
 
+const { hideMaterialMode = false, isPlyModel = false } = defineProps<{
+  hideMaterialMode?: boolean
+  isPlyModel?: boolean
+}>()
+
 const upDirection = defineModel<UpDirection>('upDirection')
 const materialMode = defineModel<MaterialMode>('materialMode')
 
@@ -46,10 +51,22 @@ const upDirectionOptions = [
 ]
 
 const materialModeOptions = computed(() => {
-  return [
-    { label: t('load3d.materialModes.original'), value: 'original' },
+  const options = [
+    { label: t('load3d.materialModes.original'), value: 'original' }
+  ]
+
+  if (isPlyModel) {
+    options.push({
+      label: t('load3d.materialModes.pointCloud'),
+      value: 'pointCloud'
+    })
+  }
+
+  options.push(
     { label: t('load3d.materialModes.normal'), value: 'normal' },
     { label: t('load3d.materialModes.wireframe'), value: 'wireframe' }
-  ]
+  )
+
+  return options
 })
 </script>