feat: onboarding optimization, invite links, admin roles, and event board

- Home: hide duplicate create/join buttons when user has no groups
- Invite links: /join/group/:id and /join/team/:id pages for one-click joining
- Admin: group admins field, ownership transfer, member management toggle
- Events: new events collection with RSVP (going/interested/maybe) and comments

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/api/groups.ts

@@ -189,6 +189,76 @@ export function subscribeGroup(groupId: string, callback: (group: Group) => void
   })
 }
 
+// 转让群主
+export async function transferGroupOwnership(groupId: string, newOwnerId: string) {
+  const user = pb.authStore.model
+  if (!user) throw new Error('未登录')
+
+  const group = await pb.collection('groups').getOne(groupId)
+  if (group.owner !== user.id) {
+    throw new Error('只有群主可以转让群组')
+  }
+
+  const admins = (group.admins as string[]) || []
+
+  // 将原群主加入 admins，新群主从 admins 中移除
+  const newAdmins = [...new Set([...admins, user.id])].filter(id => id !== newOwnerId)
+
+  return pb.collection('groups').update(groupId, {
+    owner: newOwnerId,
+    admins: newAdmins
+  })
+}
+
+// 添加管理员
+export async function addGroupAdmin(groupId: string, userId: string) {
+  const user = pb.authStore.model
+  if (!user) throw new Error('未登录')
+
+  const group = await pb.collection('groups').getOne(groupId)
+  if (group.owner !== user.id) {
+    throw new Error('只有群主可以设置管理员')
+  }
+
+  const admins = (group.admins as string[]) || []
+  if (admins.includes(userId)) {
+    throw new Error('该用户已是管理员')
+  }
+
+  return pb.collection('groups').update(groupId, {
+    admins: [...admins, userId]
+  })
+}
+
+// 移除管理员
+export async function removeGroupAdmin(groupId: string, userId: string) {
+  const user = pb.authStore.model
+  if (!user) throw new Error('未登录')
+
+  const group = await pb.collection('groups').getOne(groupId)
+  if (group.owner !== user.id) {
+    throw new Error('只有群主可以移除管理员')
+  }
+
+  const admins = (group.admins as string[]) || []
+  return pb.collection('groups').update(groupId, {
+    admins: admins.filter(id => id !== userId)
+  })
+}
+
+// 更新全员管理设置
+export async function updateGroupMemberManage(groupId: string, allow: boolean) {
+  const user = pb.authStore.model
+  if (!user) throw new Error('未登录')
+
+  const group = await pb.collection('groups').getOne(groupId)
+  if (group.owner !== user.id) {
+    throw new Error('只有群主可以修改此设置')
+  }
+
+  return pb.collection('groups').update(groupId, { allowMemberManage: allow })
+}
+
 // 订阅加入申请变更
 export function subscribeJoinRequests(groupId: string, callback: (request: JoinRequest) => void) {
   return pb.collection('join_requests').subscribe('*', (payload) => {