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>
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