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/interfaces/EventRepository.ts

@@ -0,0 +1,10 @@
+import { CalendarEvent, CreateEventDTO, UpdateEventDTO } from '@caldav/shared';
+
+export interface EventRepository {
+  findById(id: string): Promise<CalendarEvent | null>;
+  findByUserId(userId: string): Promise<CalendarEvent[]>;
+  findByDateRange(userId: string, startDate: Date, endDate: Date): Promise<CalendarEvent[]>;
+  create(userId: string, data: CreateEventDTO): Promise<CalendarEvent>;
+  update(id: string, data: UpdateEventDTO): Promise<CalendarEvent | null>;
+  delete(id: string): Promise<boolean>;
+}