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/api/cad.ts

@@ -97,3 +97,9 @@ export async function generateGltfProduction(cadFileId: string): Promise<Generat
   const res = await api.post<GenerateGltfResponse>(`/cad/${cadFileId}/generate-gltf-production`)
   return res.data
 }
+
+/** Force-reset a CAD file stuck in 'processing' to 'failed'. */
+export async function resetStuckProcessing(cadFileId: string): Promise<{ status: string; message: string }> {
+  const res = await api.post(`/cad/${cadFileId}/reset-stuck`)
+  return res.data
+}