feat(admin): 用户管理新增分组列、分组筛选与专属分组一键替换

- 新增分组列：展示用户的专属/公开分组，支持 hover 查看详情
- 新增分组筛选：下拉选择或模糊搜索分组名过滤用户
- 专属分组替换：点击专属分组弹出操作菜单，选择目标分组后
  自动授予新分组权限、迁移绑定的 Key、移除旧分组权限
- 后端新增 POST /admin/users/:id/replace-group 端点，事务内
  完成分组替换并失效认证缓存

frontend/src/components/icons/Icon.vue

@@ -86,6 +86,7 @@ const icons = {
   download: 'M4 16v1a3 3 0 003 3h10a3 3 0 003-3v-1m-4-4l-4 4m0 0l-4-4m4 4V4',
   upload: 'M3 16.5v2.25A2.25 2.25 0 005.25 21h13.5A2.25 2.25 0 0021 18.75V16.5m-13.5-9L12 3m0 0l4.5 4.5M12 3v13.5',
   filter: 'M12 3c2.755 0 5.455.232 8.083.678.533.09.917.556.917 1.096v1.044a2.25 2.25 0 01-.659 1.591l-5.432 5.432a2.25 2.25 0 00-.659 1.591v2.927a2.25 2.25 0 01-1.244 2.013L9.75 21v-6.568a2.25 2.25 0 00-.659-1.591L3.659 7.409A2.25 2.25 0 013 5.818V4.774c0-.54.384-1.006.917-1.096A48.32 48.32 0 0112 3z',
+  globe: 'M12 21a9.004 9.004 0 008.716-6.747M12 21a9.004 9.004 0 01-8.716-6.747M12 21c2.485 0 4.5-4.03 4.5-9S14.485 3 12 3m0 18c-2.485 0-4.5-4.03-4.5-9S9.515 3 12 3m0 0a8.997 8.997 0 017.843 4.582M12 3a8.997 8.997 0 00-7.843 4.582m15.686 0A11.953 11.953 0 0112 10.5c-2.998 0-5.74-1.1-7.843-2.918m15.686 0A8.959 8.959 0 0121 12c0 .778-.099 1.533-.284 2.253m0 0A17.919 17.919 0 0112 16.5c-3.162 0-6.133-.815-8.716-2.247m0 0A9.015 9.015 0 013 12c0-1.605.42-3.113 1.157-4.418',
   sort: 'M8.25 15L12 18.75 15.75 15m-7.5-6L12 5.25 15.75 9',
 
   // Security