feat: group chat owner protection — prevent removing creator, transfer ownership before leaving

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

src/lib/api.ts

@@ -360,7 +360,7 @@ export const api = {
       req<{ id: string; name: string; role: string }[]>('GET', `/api/hotels/${slug}/chat/members`),
     createGroup: (slug: string, name: string, memberIds: string[]) =>
       req<{ roomId: string }>('POST', `/api/hotels/${slug}/chat/group`, { name, memberIds }),
-    updateGroup: (slug: string, roomId: string, patch: { name?: string; avatarUrl?: string; addMemberIds?: string[]; removeMemberIds?: string[] }) =>
+    updateGroup: (slug: string, roomId: string, patch: { name?: string; avatarUrl?: string; addMemberIds?: string[]; removeMemberIds?: string[]; transferOwnerTo?: string }) =>
       req<{ ok: boolean }>('PATCH', `/api/hotels/${slug}/chat/rooms/${roomId}/group`, patch),
     editMessage: (slug: string, roomId: string, msgId: string, text: string) =>
       req<ChatMessage>('PATCH', `/api/hotels/${slug}/chat/rooms/${roomId}/messages/${msgId}`, { text }),
@@ -1363,6 +1363,7 @@ export interface ChatRoom {
   memberCount: number
   memberNames: string[] | null
   avatarUrl: string | null
+  createdBy?: string | null
 }
 
 export interface ChatReaction {