feat: GPU rendering + material matching + perf improvements

- GPU: fix Cycles device activation order — set compute_device_type
  BEFORE engine init, re-set AFTER open_mainfile wipes preferences
- GPU: remove _mark_sharp_and_seams edit-mode loop (redundant with
  Blender 5.0 shade_smooth_by_angle), saves ~200s/render on 175 parts
- Material: fix _AFN suffix mismatch — build AF-stripped mat_map keys
  and add prefix fallback in _apply_material_library (blender_render.py)
- Material: production GLB now uses get_material_library_path() which
  checks active AssetLibrary instead of empty legacy system setting
- Admin: RenderTemplateTable multi-select output types (M2M frontend)
- Admin: MaterialLibraryPanel replaced with link to Asset Libraries
- UX: move Toaster to top-left to avoid dispatch button overlap
- SQLAlchemy: add .unique() to all RenderTemplate M2M collection queries
- Logging: flush=True on all Blender progress prints, stdout reconfigure

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

frontend/src/components/cad/ThreeDViewer.tsx

@@ -24,13 +24,22 @@ import api from '../../api/client'
 export interface ThreeDViewerProps {
   cadFileId: string
   onClose: () => void
-  /** URL for the geometry-only GLB (from STL export) */
+  /** URL for the geometry-only GLB (from OCC export) */
   geometryGltfUrl?: string
-  /** URL for the production-quality GLB (from asset library render) */
+  /** URL for the production-quality GLB (Blender + PBR materials) */
   productionGltfUrl?: string
-  /** Download URLs for GLB and .blend assets */
+  /** Whether a geometry GLB exists (for hint display) */
+  hasGeometryGlb?: boolean
+  /** Whether a production GLB exists (for hint display) */
+  hasProductionGlb?: boolean
+  /** Called when the user clicks "Generate Geometry GLB" from the hint banner */
+  onGenerateGeometry?: () => void
+  /** Whether a geometry GLB generation is in progress */
+  isGeneratingGeometry?: boolean
+  /** Download URLs for assets */
   downloadUrls?: {
     glb?: string
+    production?: string
     blend?: string
   }
 }
@@ -217,9 +226,15 @@ export default function ThreeDViewer({
   onClose,
   geometryGltfUrl,
   productionGltfUrl,
+  hasGeometryGlb,
+  hasProductionGlb,
+  onGenerateGeometry,
+  isGeneratingGeometry,
   downloadUrls,
 }: ThreeDViewerProps) {
-  const [mode, setMode] = useState<ViewMode>('geometry')
+  // Default to production mode if only production GLB is available
+  const initialMode: ViewMode = productionGltfUrl && !geometryGltfUrl ? 'production' : 'geometry'
+  const [mode, setMode] = useState<ViewMode>(initialMode)
   const [wireframe, setWireframe] = useState(false)
   const [envPreset, setEnvPreset] = useState<EnvPreset>('city')
   const [capturing, setCapturing] = useState(false)
@@ -232,11 +247,11 @@ export default function ThreeDViewer({
     staleTime: 60_000,
   })
 
-  // Resolve the active model URL based on mode
+  // Resolve the active model URL: prefer selected mode, fall back to whichever URL exists
   const activeUrl =
     mode === 'production' && productionGltfUrl
       ? productionGltfUrl
-      : geometryGltfUrl
+      : geometryGltfUrl ?? productionGltfUrl
 
   const handleModelReady = useCallback(() => setModelReady(true), [])
   const handleError = useCallback((msg: string) => setLoadError(msg), [])
@@ -312,11 +327,20 @@ export default function ThreeDViewer({
           {/* Download buttons */}
           {downloadUrls?.glb && (
             <button
-              onClick={() => handleDownload(downloadUrls.glb!, `${cadFileId}.glb`)}
+              onClick={() => handleDownload(downloadUrls.glb!, `${cadFileId}_geometry.glb`)}
               className="flex items-center gap-1.5 px-3 py-1.5 rounded-md bg-gray-700 hover:bg-gray-600 text-white text-xs font-medium transition-colors"
             >
               <Download size={12} />
-              GLB
+              Geometry GLB
+            </button>
+          )}
+          {downloadUrls?.production && (
+            <button
+              onClick={() => handleDownload(downloadUrls.production!, `${cadFileId}_production.glb`)}
+              className="flex items-center gap-1.5 px-3 py-1.5 rounded-md bg-gray-700 hover:bg-gray-600 text-white text-xs font-medium transition-colors"
+            >
+              <Download size={12} />
+              Production GLB
             </button>
           )}
           {downloadUrls?.blend && (
@@ -350,6 +374,37 @@ export default function ThreeDViewer({
         </div>
       </div>
 
+      {/* Hint banners */}
+      {!hasProductionGlb && (
+        <div className="bg-amber-900/60 border-b border-amber-700/50 px-4 py-2 flex items-center gap-2 text-amber-200 text-xs shrink-0">
+          <Cpu size={13} className="shrink-0" />
+          <span>
+            <strong>No Production GLB yet.</strong> Go to the product page and click "Generate Production GLB" to create a high-quality version with PBR materials and proper mesh smoothing.
+          </span>
+        </div>
+      )}
+      {!hasGeometryGlb && hasProductionGlb && onGenerateGeometry && (
+        <div className="bg-blue-900/50 border-b border-blue-700/50 px-4 py-2 flex items-center gap-3 text-blue-200 text-xs shrink-0">
+          <Box size={13} className="shrink-0" />
+          <span>
+            <strong>Showing Production GLB.</strong> Generate a Geometry GLB to enable the mode toggle and compare geometry vs. production quality.
+          </span>
+          {isGeneratingGeometry ? (
+            <span className="flex items-center gap-1 text-blue-300 ml-auto shrink-0">
+              <Loader2 size={11} className="animate-spin" />
+              Generating…
+            </span>
+          ) : (
+            <button
+              onClick={onGenerateGeometry}
+              className="ml-auto shrink-0 px-3 py-1 rounded bg-blue-700 hover:bg-blue-600 text-white text-xs font-medium transition-colors"
+            >
+              Generate Geometry GLB
+            </button>
+          )}
+        </div>
+      )}
+
       {/* Viewport */}
       <div className="relative flex-1">
         {loadError && (