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>

backend/app/core/process_steps.py

@@ -29,7 +29,6 @@ class StepName(StrEnum):
 
     # ── GLB / asset export ────────────────────────────────────────────
     EXPORT_GLB_GEOMETRY = "export_glb_geometry"
-    EXPORT_GLB_PRODUCTION = "export_glb_production"
     EXPORT_BLEND = "export_blend"
 
     # ── STL cache ────────────────────────────────────────────────────