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

server/src/routes/group.ts

@@ -208,4 +208,125 @@ router.delete('/:id', async (req: AuthRequest, res: Response) => {
   }
 })
 
+/** 刷新邀请码（仅 owner） */
+router.post('/:id/refresh-code', async (req: AuthRequest, res: Response) => {
+  try {
+    const groupId = req.params.id
+
+    // 验证是否是群主
+    const [groupRows] = await pool.query(
+      'SELECT created_by FROM `groups` WHERE id = ?',
+      [groupId]
+    )
+    const group = (groupRows as any[])[0]
+    if (!group) {
+      return res.status(404).json({ code: 40400, message: '群组不存在' })
+    }
+    if (group.created_by !== req.userId) {
+      return res.status(403).json({ code: 40300, message: '仅群主可刷新邀请码' })
+    }
+
+    // 生成新的唯一邀请码
+    let inviteCode = generateInviteCode()
+    let attempts = 0
+    while (attempts < 10) {
+      const [existing] = await pool.query('SELECT id FROM `groups` WHERE invite_code = ?', [inviteCode])
+      if ((existing as any[]).length === 0) break
+      inviteCode = generateInviteCode()
+      attempts++
+    }
+
+    await pool.query('UPDATE `groups` SET invite_code = ? WHERE id = ?', [inviteCode, groupId])
+    res.json({ code: 0, data: { invite_code: inviteCode } })
+  } catch (err) {
+    console.error('[Group] refresh-code error:', err)
+    res.status(500).json({ code: 50000, message: '服务器错误' })
+  }
+})
+
+/** 获取成员列表 */
+router.get('/:id/members', async (req: AuthRequest, res: Response) => {
+  try {
+    const groupId = req.params.id
+
+    // 验证用户是否是群组成员
+    const [memberCheck] = await pool.query(
+      'SELECT id FROM group_members WHERE group_id = ? AND user_id = ?',
+      [groupId, req.userId]
+    )
+    if ((memberCheck as any[]).length === 0) {
+      return res.status(403).json({ code: 40300, message: '无权访问此群组' })
+    }
+
+    const [members] = await pool.query(
+      `SELECT gm.user_id, gm.role, gm.created_at as joined_at,
+              u.nickname, u.avatar_url
+       FROM group_members gm
+       LEFT JOIN users u ON gm.user_id = u.id
+       WHERE gm.group_id = ?
+       ORDER BY gm.role DESC, gm.created_at ASC`,
+      [groupId]
+    )
+
+    res.json({ code: 0, data: members })
+  } catch (err) {
+    console.error('[Group] members error:', err)
+    res.status(500).json({ code: 50000, message: '服务器错误' })
+  }
+})
+
+/** 移除成员（仅 owner） */
+router.delete('/:id/members/:userId', async (req: AuthRequest, res: Response) => {
+  try {
+    const groupId = req.params.id
+    const targetUserId = Number(req.params.userId)
+
+    // 不能移除自己
+    if (targetUserId === req.userId) {
+      return res.status(400).json({ code: 40001, message: '不能移除自己' })
+    }
+
+    // 验证是否是群主
+    const [groupRows] = await pool.query(
+      'SELECT created_by FROM `groups` WHERE id = ?',
+      [groupId]
+    )
+    const group = (groupRows as any[])[0]
+    if (!group) {
+      return res.status(404).json({ code: 40400, message: '群组不存在' })
+    }
+    if (group.created_by !== req.userId) {
+      return res.status(403).json({ code: 40300, message: '仅群主可移除成员' })
+    }
+
+    const conn = await pool.getConnection()
+    try {
+      await conn.beginTransaction()
+
+      // 清除该成员在群组的记录标签
+      await conn.query(
+        'UPDATE transactions SET group_id = NULL WHERE user_id = ? AND group_id = ?',
+        [targetUserId, groupId]
+      )
+
+      // 删除成员关系
+      await conn.query(
+        'DELETE FROM group_members WHERE group_id = ? AND user_id = ?',
+        [groupId, targetUserId]
+      )
+
+      await conn.commit()
+      res.json({ code: 0 })
+    } catch (err) {
+      await conn.rollback()
+      throw err
+    } finally {
+      conn.release()
+    }
+  } catch (err) {
+    console.error('[Group] remove member error:', err)
+    res.status(500).json({ code: 50000, message: '服务器错误' })
+  }
+})
+
 export default router