feat: 通道组并入「添加通道」表单，不再单独新建

- 去掉单独的「新建通道组」入口：添加通道表单的目标可以一次填多个
  （10.0.1.11-13:22、10.0.1.11:8080-8082、逗号分隔），预览每个地址分到的连续端口
- 表单新增「通道组」选项：不分组 / 新建通道组 / 已有组；多个目标自动放进新建的组，
  组名默认与通道名称相同；加入组时名称可不填，按「组名 (主机)」命名
- 闲置关闭、最长时长、限速、访问控制、责任人等设置对每个地址都生效，与单个通道一致
- 编辑通道时可以新建通道组并移入；组卡片上「添加地址」打开同一个表单并选好该组
- 编辑通道组只负责改名、责任人和加入已有通道
- 多个目标的连通性测试并发进行并汇总结果；网页表单补上责任人与限速
- 接口：POST /api/tunnels/batch（dry_run 预览、group_id / new_group），
  PUT /api/tunnels/{id} 支持 new_group；移除 /api/groups/preview 及组接口里的批量建通道

tools/ui-snapshots/main.swift

@@ -259,14 +259,15 @@ MainActor.assumeIsolated {
     render("readme-edit", CGSize(width: 490, height: 760), TunnelEditSheet(vm: demo, tunnel: demo.tunnels[0], isPresented: yes))
     let g = demo.groups[0]
     render("group-card", CGSize(width: 980, height: 330), GroupCardView(group: g, members: demo.members(of: g), visible: demo.members(of: g), vm: demo,
-        onEdit: {}, onInvite: {}, onViewClients: { _ in }, onEditMember: { _ in }, onInviteMember: { _ in }, onMemberClients: { _ in }).padding(20))
+        onEdit: {}, onAddMember: {}, onInvite: {}, onViewClients: { _ in }, onEditMember: { _ in }, onInviteMember: { _ in }, onMemberClients: { _ in }).padding(20))
     render("group-card-dark", CGSize(width: 980, height: 330), dark: true, GroupCardView(group: g, members: demo.members(of: g), visible: demo.members(of: g), vm: demo,
-        onEdit: {}, onInvite: {}, onViewClients: { _ in }, onEditMember: { _ in }, onInviteMember: { _ in }, onMemberClients: { _ in }).padding(20))
+        onEdit: {}, onAddMember: {}, onInvite: {}, onViewClients: { _ in }, onEditMember: { _ in }, onInviteMember: { _ in }, onMemberClients: { _ in }).padding(20))
     render("group-card-narrow", CGSize(width: 720, height: 360), GroupCardView(group: g, members: demo.members(of: g), visible: demo.members(of: g), vm: demo,
-        onEdit: {}, onInvite: {}, onViewClients: { _ in }, onEditMember: { _ in }, onInviteMember: { _ in }, onMemberClients: { _ in }).padding(20))
-    render("group-sheet-new", CGSize(width: 560, height: 640), GroupEditSheet(vm: demo, group: nil, isPresented: yes,
-        initialName: "订单服务", initialHosts: "10.0.3.11-13", initialPorts: "22, 8080"))
-    render("group-sheet-edit", CGSize(width: 560, height: 520), GroupEditSheet(vm: demo, group: g, isPresented: yes))
+        onEdit: {}, onAddMember: {}, onInvite: {}, onViewClients: { _ in }, onEditMember: { _ in }, onInviteMember: { _ in }, onMemberClients: { _ in }).padding(20))
+    render("group-add-batch", CGSize(width: 490, height: 860), TunnelEditSheet(vm: demo, tunnel: nil, isPresented: yes,
+        draftName: "订单服务", draftTarget: "10.0.3.11-13:22, 10.0.3.11-13:8080"))
+    render("group-add-member", CGSize(width: 490, height: 780), TunnelEditSheet(vm: demo, tunnel: nil, isPresented: yes, groupId: g.id))
+    render("group-sheet-edit", CGSize(width: 520, height: 420), GroupEditSheet(vm: demo, group: g, isPresented: yes))
     render("group-invite", CGSize(width: 560, height: 300), InviteSheet(vm: demo, scope: .group(g.id), autoGenerate: true, isPresented: yes))
     render("group-access", CGSize(width: 760, height: 560), ClientDetailsSheet(vm: demo, scope: .group(g.id), initialTab: 2, isPresented: yes))
     render("group-online", CGSize(width: 760, height: 400), ClientDetailsSheet(vm: demo, scope: .group(g.id), initialTab: 0, isPresented: yes))