fix: media thumbnails, product dimensions, inline 3D viewer, GLB export

Bug A: Media Library thumbnails were gray because <img src> cannot send
JWT auth headers. Added useAuthBlob() hook (fetch + createObjectURL) in
MediaBrowser.tsx. Also fixed publish_asset Celery task to populate
product_id + cad_file_id on MediaAsset for thumbnail fallback resolution.

Bug B: Product dimensions now shown in Product Details card with Ruler
icon and "from CAD" label when cad_mesh_attributes.dimensions_mm exists.

Bug C: Replaced 128×128 CAD thumbnail with InlineCadViewer component.
Queries gltf_geometry MediaAssets, fetches GLB via auth fetch → blob URL
→ Three.js Canvas with OrbitControls. Falls back to thumbnail + "Load 3D
Model" button. Polling when GLB generation is in progress.

Bug D: trimesh was in [cad] optional extra but Dockerfile only installed
[dev]. Changed to pip install -e ".[dev,cad]" — trimesh now available in
backend container, GLB + Colors export works.

Also added bbox extraction (STL-first numpy parsing) in render_step_thumbnail
and admin "Re-extract CAD Metadata" bulk endpoint.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/cad/ThreeDViewer.tsx

@@ -8,6 +8,7 @@ import {
   type ErrorInfo,
   type ReactNode,
 } from 'react'
+import { useQuery } from '@tanstack/react-query'
 import { Canvas, useThree, useFrame } from '@react-three/fiber'
 import { OrbitControls, useGLTF, Environment } from '@react-three/drei'
 import { toast } from 'sonner'
@@ -225,6 +226,12 @@ export default function ThreeDViewer({
   const [loadError, setLoadError] = useState<string | null>(null)
   const [modelReady, setModelReady] = useState(false)
 
+  const { data: settings3d } = useQuery({
+    queryKey: ['admin-settings'],
+    queryFn: () => api.get('/admin/settings').then(r => r.data),
+    staleTime: 60_000,
+  })
+
   // Resolve the active model URL based on mode
   const activeUrl =
     mode === 'production' && productionGltfUrl
@@ -362,7 +369,7 @@ export default function ThreeDViewer({
         {!modelReady && !loadError && <LoadingOverlay />}
 
         <Canvas
-          camera={{ position: [0, 2, 5], fov: 45 }}
+          camera={{ position: [0, 0.1, 0.3], fov: 45 }}
           gl={{ preserveDrawingBuffer: true }}
           style={{ width: '100%', height: '100%', background: '#111827' }}
         >
@@ -383,7 +390,13 @@ export default function ThreeDViewer({
             </GltfErrorBoundary>
           )}
 
-          <OrbitControls enablePan enableZoom enableRotate minDistance={0.3} maxDistance={100} />
+          <OrbitControls
+            enablePan
+            enableZoom
+            enableRotate
+            minDistance={settings3d?.viewer_min_distance ?? 0.001}
+            maxDistance={settings3d?.viewer_max_distance ?? 50}
+          />
           <Environment preset={envPreset} />
 
           {capturing && (