refactor: rename thumbnail_rendering queue to asset_pipeline

The queue handles far more than thumbnails: OCC tessellation, USD master
generation, GLB production, order line renders, and workflow renders.
asset_pipeline better reflects its role as the render-worker's primary queue.

Updated all references in: task decorators, celery_app.py, beat_tasks.py,
docker-compose.yml worker command, worker.py MONITORED_QUEUES, admin.py,
CLAUDE.md, LEARNINGS.md, Dockerfile, helpTexts.ts, test files,
and all .claude/commands/*.md skill files.

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

backend/app/services/part_key_service.py

@@ -105,6 +105,10 @@ def build_scene_manifest(cad_file, usd_asset=None) -> dict:
         object_names: list[str] = cad_file.parsed_objects.get("objects") or []
         seen_keys: set[str] = set()
         for source_name in object_names:
+            # Fallback: USD master not yet generated. Use source_name as xcaf_path proxy.
+            # Note: slugs produced here may differ from what export_step_to_usd.py will
+            # produce for unnamed parts (which use sha256 of the XCAF hierarchy path).
+            # Named parts will match once USD master is generated.
             part_key = generate_part_key(source_name, source_name, seen_keys)
             effective_material, provenance = _resolve_material(
                 part_key, source_name, manual, resolved, source