refactor(P11+P12): codebase hygiene — CLAUDE.md rewrite, type safety, dead code removal

- Rewrite CLAUDE.md to match current 8-service architecture (was 11, 5 deleted)
- Remove all as-any casts in OrderDetail.tsx (9 casts → 0)
- Add cad_parsed_objects/cad_part_materials to OrderItem interface
- Rename require_admin → require_global_admin across 6 router files (22 calls)
- Remove EXPORT_GLB_PRODUCTION enum + generate_gltf_production_task (dead code)
- Remove worker-thumbnail from ALLOWED_SERVICES, replace Flamenco link
- Delete obsolete PLAN.md (1455 lines) and PLAN_REFACTOR.md (1174 lines)
- Fix digit-only USD prim names with p_ prefix

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

render-worker/scripts/export_step_to_usd.py

@@ -63,6 +63,9 @@ def _generate_part_key(xcaf_path: str, source_name: str, existing_keys: set) ->
     if not slug:
         slug = f"part_{hashlib.sha256(xcaf_path.encode()).hexdigest()[:8]}"
     slug = slug[:50]
+    # USD prim names cannot start with a digit
+    if slug and slug[0].isdigit():
+        slug = f"p_{slug}"
     key = slug
     n = 2
     while key in existing_keys: