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

packages/shared/src/models/CalendarEvent.ts

@@ -0,0 +1,33 @@
+export interface CalendarEvent {
+  id: string;
+  userId: string;
+  title: string;
+  description?: string;
+  startTime: Date;
+  endTime: Date;
+  note?: string;
+  isRecurring?: boolean;
+  recurrenceRule?: string;
+  createdAt?: Date;
+  updatedAt?: Date;
+}
+
+export interface CreateEventDTO {
+  title: string;
+  description?: string;
+  startTime: Date;
+  endTime: Date;
+  note?: string;
+  isRecurring?: boolean;
+  recurrenceRule?: string;
+}
+
+export interface UpdateEventDTO {
+  title?: string;
+  description?: string;
+  startTime?: Date;
+  endTime?: Date;
+  note?: string;
+  isRecurring?: boolean;
+  recurrenceRule?: string;
+}

packages/shared/src/models/ChatMessage.ts

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+import { CreateEventDTO } from './CalendarEvent';
+
+export type MessageSender = 'user' | 'assistant';
+
+export interface ChatMessage {
+  id: string;
+  conversationId: string;
+  sender: MessageSender;
+  content: string;
+  proposedEvent?: CreateEventDTO;
+  createdAt?: Date;
+}
+
+export interface Conversation {
+  id: string;
+  userId: string;
+  createdAt?: Date;
+  updatedAt?: Date;
+}
+
+export interface SendMessageDTO {
+  conversationId?: string;
+  content: string;
+}
+
+export interface CreateMessageDTO {
+  sender: MessageSender;
+  content: string;
+  proposedEvent?: CreateEventDTO;
+}
+
+export interface GetMessagesOptions {
+  before?: string;  // Message ID - load messages before this one
+  limit?: number;   // Default: 20
+}
+
+export interface ChatResponse {
+  message: ChatMessage;
+  conversationId: string;
+}
+
+export interface ConversationSummary {
+  id: string;
+  lastMessage?: ChatMessage;
+  createdAt?: Date;
+}

packages/shared/src/models/User.ts

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+export interface User {
+  id: string;
+  email: string;
+  displayName: string;
+  passwordHash?: string;
+  createdAt?: Date;
+  updatedAt?: Date;
+}
+
+export interface CreateUserDTO {
+  email: string;
+  displayName: string;
+  password: string;
+}
+
+export interface LoginDTO {
+  email: string;
+  password: string;
+}
+
+export interface AuthResponse {
+  user: Omit<User, 'passwordHash'>;
+  accessToken: string;
+  refreshToken?: string;
+}

packages/shared/src/models/index.ts

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+export * from './User';
+export * from './CalendarEvent';
+export * from './ChatMessage';