feat(M5-M7): embed canonical material names in USD via customData + pxr direct read

- export_step_to_usd.py: accept --material_map CLI arg, write
  schaeffler:canonicalMaterialName as customData on each Mesh prim,
  fix geometry transform (strip shape Location before face exploration,
  apply both face_loc and shape_loc sequentially)
- import_usd.py: after Blender USD import, use pxr to read customData
  directly from the USD file — builds {part_key: material_name} lookup
  (Blender ignores STRING primvars and customData, but pxr reads both)
- _blender_materials.py: add apply_material_library_direct() for exact
  dict-based material assignment without name-matching heuristics
- _blender_scene_setup.py: prefer direct USD lookup, fall back to
  name-matching for legacy USD files without material metadata
- export_glb.py (generate_usd_master_task): resolve material_map via
  material_service.resolve_material_map() and pass to subprocess;
  include material hash in cache key for invalidation
- ROADMAP.md: update P5 status, add M5-M7 milestones

Tested: 3/3 parts matched (ans_lfs120), 172/175 parts matched
(F-802007.TR4-D1-H122AG). Previous: 0/25 matched.

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

.claude/commands/debug-render.md

@@ -12,7 +12,7 @@ process_step_file  [queue: step_processing, worker container]
   → parses STEP objects, stores parsed_objects
   → queues render_step_thumbnail
 
-render_step_thumbnail  [queue: thumbnail_rendering, render-worker container]
+render_step_thumbnail  [queue: asset_pipeline, render-worker container]
   → backend/app/domains/pipeline/tasks/render_thumbnail.py
   → subprocess: export_step_to_gltf.py  (OCC/GMSH tessellation → geometry GLB)
   → subprocess: export_gltf.py  (Blender: materials, seams, sharp edges → production GLB)
@@ -123,7 +123,7 @@ from app.tasks.celery_app import celery_app
 celery_app.send_task(
     'app.domains.pipeline.tasks.render_thumbnail.render_step_thumbnail',
     args=['[cad_file_id]'],
-    queue='thumbnail_rendering'
+    queue='asset_pipeline'
 )"
 ```