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/ProductDetail.tsx

@@ -1,10 +1,10 @@
 import { useState, useCallback, useEffect, Fragment, useMemo } from 'react'
-import { useParams, Link } from 'react-router-dom'
+import { useParams, Link, useNavigate } from 'react-router-dom'
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query'
 import { useDropzone } from 'react-dropzone'
 import {
   ArrowLeft, Pencil, Save, X, Box, Image,
-  RotateCcw, RefreshCw, Upload, ChevronDown, ChevronRight, Wand2, Download, Plus, Trash2, Filter,
+  RotateCcw, RefreshCw, Upload, ChevronDown, ChevronRight, Wand2, Download, Plus, Trash2, Filter, Cuboid,
 } from 'lucide-react'
 import { toast } from 'sonner'
 import {
@@ -18,7 +18,7 @@ import { listMaterials } from '../api/materials'
 import MaterialInput from '../components/shared/MaterialInput'
 import MaterialWizard from '../components/MaterialWizard'
 import { useAuthStore } from '../store/auth'
-import { downloadStl, generateStl } from '../api/cad'
+import { downloadStl, generateStl, generateGltfGeometry } from '../api/cad'
 
 function CadStatusBadge({ status }: { status: string | null }) {
   if (!status) return (
@@ -48,6 +48,7 @@ const META_FIELDS: Array<{ key: keyof Product; label: string }> = [
 
 export default function ProductDetailPage() {
   const { id } = useParams<{ id: string }>()
+  const navigate = useNavigate()
   const qc = useQueryClient()
   const user = useAuthStore((s) => s.user)
   const isPrivileged = user?.role === 'admin' || user?.role === 'project_manager'
@@ -552,6 +553,30 @@ export default function ProductDetailPage() {
                     </button>
                   </>
                 )}
+                {product.cad_file_id && (
+                  <button
+                    className="btn-secondary text-xs"
+                    onClick={() => navigate(`/cad/${product.cad_file_id}`)}
+                    title="Open interactive 3D viewer"
+                  >
+                    <Cuboid size={12} />
+                    View 3D
+                  </button>
+                )}
+                {product.cad_file_id && isPrivileged && (
+                  <button
+                    className="btn-secondary text-xs"
+                    onClick={() =>
+                      generateGltfGeometry(product.cad_file_id!)
+                        .then(() => toast.info('GLB geometry export queued'))
+                        .catch(() => toast.error('Failed to queue GLB export'))
+                    }
+                    title="Export geometry-only GLB from cached STL (trimesh, no Blender). Requires STL cache."
+                  >
+                    <Download size={12} />
+                    Generate GLB
+                  </button>
+                )}
                 {product.cad_file_id && isPrivileged && (
                   <div className="flex flex-col gap-1 pt-1 border-t border-border-light">
                     <p className="text-xs text-content-muted font-medium">STL</p>