feat: 群组管理页面优化 + 分类管理图标修复

- 创建/加入群组合并为 Tab 切换卡片
- 群主可刷新邀请码（后端+前端完整链路）
- 群主可管理成员：查看列表、移除成员
- 新增后端 API：refresh-code / members / remove-member
- 修复分类管理页 FAB 按钮缺少 plus 图标
- 新增 plus/refresh 图标资源

client/src/stores/group.ts

@@ -97,6 +97,32 @@ export const useGroupStore = defineStore('group', () => {
     await fetchGroups()
   }
 
+  /** 刷新邀请码（群主） */
+  async function refreshInviteCode(groupId: number) {
+    const result = await api.refreshInviteCode(groupId)
+    // 更新本地 groups 中的 invite_code
+    const group = groups.value.find(g => g.id === groupId)
+    if (group) {
+      group.invite_code = result.invite_code
+    }
+    return result
+  }
+
+  /** 获取成员列表 */
+  async function fetchGroupMembers(groupId: number) {
+    return await api.getGroupMembers(groupId)
+  }
+
+  /** 移除成员（群主） */
+  async function removeMember(groupId: number, userId: number) {
+    await api.removeMember(groupId, userId)
+    // 更新本地成员数
+    const group = groups.value.find(g => g.id === groupId)
+    if (group && group.member_count > 0) {
+      group.member_count--
+    }
+  }
+
   /** 初始化：从本地存储恢复选中状态 */
   function init() {
     const saved = uni.getStorageSync('xc:currentGroupId')
@@ -108,6 +134,7 @@ export const useGroupStore = defineStore('group', () => {
   return {
     groups, loading, currentGroupId, currentGroup, isGroupMode,
     switchToPersonal, switchToGroup, refreshAll,
-    fetchGroups, createGroup, joinGroup, leaveGroup, deleteGroup, init
+    fetchGroups, createGroup, joinGroup, leaveGroup, deleteGroup,
+    refreshInviteCode, fetchGroupMembers, removeMember, init
   }
 })