feat(N): workflow pipeline, 3D viewer, worker management, QC tests

- workflow_builder.py: fix broken stubs, add render_order_line_still_task
  (resolves step_path from DB instead of passing order_line_id as step_path)
- domains/rendering/tasks.py: add render_order_line_still_task,
  export_gltf_for_order_line_task, export_blend_for_order_line_task,
  generate_gltf_geometry_task (trimesh STL→GLB, no Blender needed)
- tasks/step_tasks.py: add generate_gltf_geometry_task for CadFile GLB export
- cad router: POST /{id}/generate-gltf-geometry endpoint (admin/PM)
- worker router: GET /celery-workers + POST /scale (docker compose subprocess)
- Dockerfile: pip install -e "[dev]" to enable pytest
- docker-compose.yml: docker socket + compose file mount on backend
- ThreeDViewer.tsx: mode toggle (geometry/production), wireframe, env presets,
  download buttons (GLB + .blend)
- CadPreview.tsx: load gltf_geometry/gltf_production/blend_production assets
  from MediaAsset table and pass URLs to ThreeDViewer
- ProductDetail.tsx: "View 3D" button → /cad/:id, "Generate GLB" button
- media router/service: cad_file_id filter on GET /api/media
- WorkerManagement.tsx: new page with worker status, queue depth, scale controls
- App.tsx + Layout.tsx: /workers route + sidebar link (admin/PM)
- tests: test_rendering_service.py, test_orders_service.py (backend)
- tests: WorkerActivity.test.tsx, WorkerManagement.test.tsx (frontend)

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

frontend/src/pages/CadPreview.tsx

@@ -1,36 +1,64 @@
 import { useParams, useNavigate } from 'react-router-dom'
-import { ArrowLeft } from 'lucide-react'
+import { useQuery } from '@tanstack/react-query'
 import ThreeDViewer from '../components/cad/ThreeDViewer'
+import { getMediaAssets } from '../api/media'
 
 /**
  * Route: /cad/:id
  *
- * Renders the full-screen 3D viewer for a specific CAD file.
- * When the viewer is closed the user is navigated back.
+ * Full-screen 3D viewer for a CAD file.
+ * Passes production GLB URL if a gltf_geometry MediaAsset exists for this CAD file.
  */
 export default function CadPreviewPage() {
   const { id } = useParams<{ id: string }>()
   const navigate = useNavigate()
 
+  // Load any geometry GLB that was generated for this CAD file
+  const { data: gltfAssets } = useQuery({
+    queryKey: ['media-assets', id, 'gltf_geometry'],
+    queryFn: () => getMediaAssets({ cad_file_id: id!, asset_type: 'gltf_geometry' }),
+    enabled: !!id,
+    staleTime: 30_000,
+  })
+
+  // Load production GLB if available
+  const { data: productionAssets } = useQuery({
+    queryKey: ['media-assets', id, 'gltf_production'],
+    queryFn: () => getMediaAssets({ cad_file_id: id!, asset_type: 'gltf_production' }),
+    enabled: !!id,
+    staleTime: 30_000,
+  })
+
+  // Load blend assets for download
+  const { data: blendAssets } = useQuery({
+    queryKey: ['media-assets', id, 'blend_production'],
+    queryFn: () => getMediaAssets({ cad_file_id: id!, asset_type: 'blend_production' }),
+    enabled: !!id,
+    staleTime: 30_000,
+  })
+
   if (!id) {
     return (
-      <div className="flex flex-col items-center justify-center h-full text-content-muted gap-4 p-8">
-        <p className="text-lg">No CAD file ID provided.</p>
-        <button
-          onClick={() => navigate(-1)}
-          className="flex items-center gap-2 text-sm text-accent hover:underline"
-        >
-          <ArrowLeft size={16} />
-          Go back
-        </button>
+      <div className="flex items-center justify-center h-full text-content-muted p-8">
+        <p>No CAD file ID provided.</p>
       </div>
     )
   }
 
+  const latestGltf = gltfAssets?.[0]
+  const latestProduction = productionAssets?.[0]
+  const latestBlend = blendAssets?.[0]
+
   return (
     <ThreeDViewer
       cadFileId={id}
       onClose={() => navigate(-1)}
+      geometryGltfUrl={latestGltf?.download_url ?? undefined}
+      productionGltfUrl={latestProduction?.download_url ?? undefined}
+      downloadUrls={{
+        glb: latestGltf?.download_url ?? undefined,
+        blend: latestBlend?.download_url ?? undefined,
+      }}
     />
   )
 }