* feat(groups): add drag-and-drop reorder for group list
- Add PUT /api/groups/reorder endpoint with transactional batch update
- Implement drag-and-drop UI in GroupList.vue with visual feedback
- Support touch device detection and search mode restrictions
- Add i18n messages for zh-CN, en-US, ja-JP
* feat(groups): enhance group reordering with database locking and refresh event
* feat(groups): refactor group item reference handling in drag-and-drop
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Co-authored-by: QLHazyCoder1 <qzec571@163.com>