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>

render-worker/scripts/turntable_render.py

@@ -2,7 +2,7 @@
 
 Usage (from Blender):
   blender --background --python turntable_render.py -- \
-    <stl_path> <frames_dir> <frame_count> <degrees> <width> <height> \
+    <glb_path> <frames_dir> <frame_count> <degrees> <width> <height> \
     <engine> <samples> <part_colors_json> \
     [template_path] [target_collection] [material_library_path] [material_map_json]
 """
@@ -88,7 +88,7 @@ def _apply_rotation(parts, rx, ry, rz):
     """Apply Euler XYZ rotation (degrees) to all parts by modifying matrix_world.
 
     Rotates around world origin, which equals the assembly centre because
-    _import_stl already centres parts there.  Applied before material assignment
+    _import_glb already centres parts there.  Applied before material assignment
     and camera/bbox calculations so everything downstream sees the final pose.
     """
     if not parts or (rx == 0.0 and ry == 0.0 and rz == 0.0):