Add pending accessories section to both single-code and multi-code boxing
modes. Accessories display with orange styling and a "加入本箱" button that
calls saveBoxRecord with item_type=accessory. Extend API service with
PendingAccessory model, itemType fields on data classes, and optional
accessory_id parameter on saveBoxRecord. Show accessories with visual
indicator (wrench icon + orange background) in boxing detail page.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Extract large methods from _BoxingPageState into 6 part files:
- boxing_scan_part.dart: scan handling and auto-scan processing
- boxing_submit_part.dart: submit/update/delete API calls
- boxing_box_mutation_part.dart: box item mutations
- boxing_single_ops_part.dart: single-code boxing operations
- boxing_multi_ops_part.dart: multi-code boxing operations
- boxing_status_part.dart: status bar management
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
