Update group member creation to include addedBy and addedAt fields.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 9111ef36-26c8-4085-84ca-a35dc1fec1b5
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/7083d608-d6d3-4a6a-9a27-6286c5109627/5a682ad9-3416-4b63-8a79-88b09e35d0e7.jpg

server/storage.ts

@@ -313,13 +313,14 @@ export class MemStorage implements IStorage {
   
   async addGroupMember(member: InsertGroupMember): Promise<GroupMember> {
     const numId = this.groupMemberIdCounter++;
-    const createdAt = new Date();
+    const addedAt = new Date();
     const newMember: GroupMember = {
       id: numId.toString(),
       groupId: member.groupId,
       memberId: member.memberId,
       memberType: member.memberType,
-      createdAt
+      addedBy: member.addedBy,
+      addedAt
     };
     this.groupMembersMap.set(numId, newMember);
     return newMember;