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/services/AuthService.ts

@@ -0,0 +1,24 @@
+import { User, CreateUserDTO, LoginDTO, AuthResponse } from '@caldav/shared';
+import { UserRepository } from './interfaces';
+import * as jwt from '../utils/jwt';
+import * as password from '../utils/password';
+
+export class AuthService {
+  constructor(private userRepo: UserRepository) {}
+
+  async login(data: LoginDTO): Promise<AuthResponse> {
+    throw new Error('Not implemented');
+  }
+
+  async register(data: CreateUserDTO): Promise<AuthResponse> {
+    throw new Error('Not implemented');
+  }
+
+  async refreshToken(refreshToken: string): Promise<AuthResponse> {
+    throw new Error('Not implemented');
+  }
+
+  async logout(userId: string): Promise<void> {
+    throw new Error('Not implemented');
+  }
+}