implement backend skeleton with MongoDB and Claude AI integration

- Add controllers (Auth, Chat, Event) with placeholder implementations
- Add services (Auth, Chat, Event) with business logic interfaces
- Add repositories with MongoDB/Mongoose models (User, Event, Chat)
- Add middleware for JWT authentication
- Add Claude AI adapter implementing AIProvider interface
- Add utility modules for JWT and password handling
- Add shared types and DTOs for User, CalendarEvent, ChatMessage
- Configure routes with proper endpoint structure
- Update app.ts with dependency injection setup
- Add required dependencies: mongoose, bcrypt, jsonwebtoken, @anthropic-ai/sdk

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

@@ -0,0 +1,17 @@
+import { User } from '@caldav/shared';
+import { UserRepository, CreateUserData } from '../../services/interfaces';
+import { UserModel } from './models';
+
+export class MongoUserRepository implements UserRepository {
+  async findById(id: string): Promise<User | null> {
+    throw new Error('Not implemented');
+  }
+
+  async findByEmail(email: string): Promise<User | null> {
+    throw new Error('Not implemented');
+  }
+
+  async create(data: CreateUserData): Promise<User> {
+    throw new Error('Not implemented');
+  }
+}