extend chat model with CRUD actions for event changes

- Add ProposedEventChange type with create/update/delete actions
- Replace proposedEvent with proposedChange in ChatMessage
- Add currentDate to AIContext for time-aware AI responses
- Add AI test endpoint for development (/api/ai/test)
- Fix MongoUserRepository type safety with explicit toUser mapping
- Update CLAUDE.md documentation

apps/server/src/repositories/mongo/MongoUserRepository.ts

@@ -1,19 +1,29 @@
 import { User } from '@caldav/shared';
 import { UserRepository, CreateUserData } from '../../services/interfaces';
-import { UserModel } from './models';
+import { UserModel, UserDocument } from './models';
 
 export class MongoUserRepository implements UserRepository {
+  private toUser(doc: UserDocument): User {
+    return {
+      id: doc._id.toString(),
+      email: doc.email,
+      displayName: doc.displayName,
+      createdAt: doc.createdAt,
+      updatedAt: doc.updatedAt,
+    };
+  }
+
   async findById(id: string): Promise<User | null> {
     throw new Error('Not implemented');
   }
 
   async findByEmail(email: string): Promise<User | null> {
     const user = await UserModel.findOne({ email: email.toLowerCase() });
-    return user ? user.toJSON() as User : null;
+    return user ? this.toUser(user) : null;
   }
 
   async create(data: CreateUserData): Promise<User> {
     const user = await UserModel.create(data);
-    return user.toJSON() as User;
+    return this.toUser(user);
   }
 }