feat: add skeleton visualization toggle for 3D models (#7857)

## Summary

For better support animation 3d model custon node, such as
https://github.com/jtydhr88/ComfyUI-HY-Motion1, add ability to show/hide
skeleton bones in Load3D nodes for models with skeletal animation. Uses
THREE.SkeletonHelper with root bone detection to properly support both
FBX and GLB model formats.

## Screenshots


https://github.com/user-attachments/assets/df9de4a6-549e-4227-aa00-8859d71f43d1

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7857-feat-add-skeleton-visualization-toggle-for-3D-models-2e06d73d365081a39f49f81f72657a70)
by [Unito](https://www.unito.io)

src/components/load3d/Load3DControls.vue

@@ -58,8 +58,10 @@
         v-if="showModelControls"
         v-model:material-mode="modelConfig!.materialMode"
         v-model:up-direction="modelConfig!.upDirection"
+        v-model:show-skeleton="modelConfig!.showSkeleton"
         :hide-material-mode="isSplatModel"
         :is-ply-model="isPlyModel"
+        :has-skeleton="hasSkeleton"
       />
 
       <CameraControls
@@ -99,9 +101,14 @@ import type {
 } from '@/extensions/core/load3d/interfaces'
 import { cn } from '@/utils/tailwindUtil'
 
-const { isSplatModel = false, isPlyModel = false } = defineProps<{
+const {
+  isSplatModel = false,
+  isPlyModel = false,
+  hasSkeleton = false
+} = defineProps<{
   isSplatModel?: boolean
   isPlyModel?: boolean
+  hasSkeleton?: boolean
 }>()
 
 const sceneConfig = defineModel<SceneConfig>('sceneConfig')