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/ChatService.ts

@@ -0,0 +1,30 @@
+import { ChatMessage, ChatResponse, SendMessageDTO, CalendarEvent, ConversationSummary, GetMessagesOptions } from '@caldav/shared';
+import { ChatRepository, EventRepository, AIProvider } from './interfaces';
+
+export class ChatService {
+  constructor(
+    private chatRepo: ChatRepository,
+    private eventRepo: EventRepository,
+    private aiProvider: AIProvider
+  ) {}
+
+  async processMessage(userId: string, data: SendMessageDTO): Promise<ChatResponse> {
+    throw new Error('Not implemented');
+  }
+
+  async confirmEvent(userId: string, conversationId: string, messageId: string): Promise<CalendarEvent> {
+    throw new Error('Not implemented');
+  }
+
+  async rejectEvent(conversationId: string, messageId: string): Promise<void> {
+    throw new Error('Not implemented');
+  }
+
+  async getConversations(userId: string): Promise<ConversationSummary[]> {
+    throw new Error('Not implemented');
+  }
+
+  async getConversation(userId: string, conversationId: string, options?: GetMessagesOptions): Promise<ChatMessage[]> {
+    throw new Error('Not implemented');
+  }
+}