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>

backend/app/domains/pipeline/tasks/export_glb.py

@@ -557,6 +557,7 @@ def generate_usd_master_task(self, cad_file_id: str) -> dict:
     from app.models.cad_file import CadFile
     from app.models.system_setting import SystemSetting
     from app.domains.products.models import Product
+    from app.services.material_service import resolve_material_map
 
     pl = PipelineLogger(task_id=self.request.id)
     pl.step_start("usd_master", {"cad_file_id": cad_file_id})
@@ -593,12 +594,26 @@ def generate_usd_master_task(self, cad_file_id: str) -> dict:
             ).scalar_one_or_none()
 
             color_map: dict[str, str] = {}
+            raw_mat_map: dict[str, str] = {}
             if product and product.cad_part_materials:
                 for entry in product.cad_part_materials:
                     part_name = entry.get("part_name") or entry.get("name", "")
                     hex_color = entry.get("hex_color") or entry.get("color", "")
                     if part_name and hex_color:
                         color_map[part_name] = hex_color
+                    # Build raw material map for resolve_material_map
+                    raw_material = entry.get("material", "")
+                    if part_name and raw_material:
+                        raw_mat_map[part_name] = raw_material
+
+            # Resolve raw material names to SCHAEFFLER library names via aliases
+            material_map: dict[str, str] = {}
+            if raw_mat_map:
+                material_map = resolve_material_map(raw_mat_map)
+                logger.info(
+                    "generate_usd_master_task: resolved %d material(s) for material_map",
+                    len(material_map),
+                )
 
             settings_rows = sess.execute(_sel(SystemSetting)).scalars().all()
             sys_settings = {s.key: s.value for s in settings_rows}
@@ -611,9 +626,14 @@ def generate_usd_master_task(self, cad_file_id: str) -> dict:
             from app.domains.products.cache_service import compute_step_hash as _compute_step_hash_usd
             _current_hash_usd = _compute_step_hash_usd(str(step_path))
 
-            # Composite cache key includes deflection settings so changing them invalidates cache
+            # Composite cache key includes deflection settings and material_map
+            # so changing either invalidates cache (material primvars are baked into USD)
+            import hashlib as _hashlib_cache
+            _mat_hash = _hashlib_cache.md5(
+                _json.dumps(material_map, sort_keys=True).encode()
+            ).hexdigest()[:12] if material_map else "none"
             effective_cache_key = (
-                f"{_current_hash_usd}:{linear_deflection}:{angular_deflection}:{sharp_threshold}"
+                f"{_current_hash_usd}:{linear_deflection}:{angular_deflection}:{sharp_threshold}:{_mat_hash}"
                 if _current_hash_usd else None
             )
 
@@ -670,6 +690,8 @@ def generate_usd_master_task(self, cad_file_id: str) -> dict:
             "--sharp_threshold", str(sharp_threshold),
             "--cad_file_id", cad_file_id,
         ]
+        if material_map:
+            cmd += ["--material_map", _json.dumps(material_map)]
 
         log_task_event(
             self.request.id,