feat: add initial backend and frontend structure with models, DTOs, and WebSocket events

packages/shared/src/api/dto.ts

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+/**
+ * Shared API DTOs
+ * Used by backend for validation and frontend for type safety
+ */
+
+// Character DTOs
+export interface CreateCharacterDto {
+  name: string;
+  personalityPrompt: string;
+  backstory?: string;
+  attributes?: Record<string, unknown>;
+  avatarUrl?: string;
+  config?: Record<string, unknown>;
+}
+
+export interface UpdateCharacterDto extends Partial<CreateCharacterDto> {}
+
+export interface CharacterResponseDto {
+  id: string;
+  name: string;
+  avatarUrl?: string;
+  personalityPrompt: string;
+  backstory?: string;
+  attributes: Record<string, unknown>;
+  config: Record<string, unknown>;
+  isPublic: boolean;
+  createdAt: string;
+  updatedAt: string;
+}
+
+// Conversation DTOs
+export interface CreateConversationDto {
+  characterId: string;
+  title?: string;
+}
+
+export interface ConversationResponseDto {
+  id: string;
+  title?: string;
+  characterId: string;
+  messageCount: number;
+  totalTokens: number;
+  createdAt: string;
+  updatedAt: string;
+}
+
+// Message DTOs
+export interface CreateMessageDto {
+  content: string;
+}
+
+export interface MessageResponseDto {
+  id: string;
+  role: 'user' | 'assistant' | 'system';
+  content: string;
+  tokensUsed?: number;
+  model?: string;
+  metadata?: Record<string, unknown>;
+  createdAt: string;
+}
+
+// Auth DTOs
+export interface LoginDto {
+  username: string;
+  password: string;
+}
+
+export interface RegisterDto {
+  email: string;
+  username: string;
+  password: string;
+}
+
+export interface AuthResponseDto {
+  accessToken: string;
+  refreshToken: string;
+  expiresIn: number;
+  user: UserResponseDto;
+}
+
+export interface UserResponseDto {
+  id: string;
+  email: string;
+  username: string;
+  role: 'USER' | 'ADMIN';
+}

packages/shared/src/api/index.ts

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+export * from './dto.js';

packages/shared/src/index.ts

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+export * from './websocket/index.js';
+export * from './api/index.js';

packages/shared/src/websocket/events.ts

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+/**
+ * WebSocket Event Types
+ * Shared between frontend and backend for type-safe communication
+ */
+
+export enum WebSocketEventType {
+  // Client -> Server
+  JOIN_CONVERSATION = 'JOIN_CONVERSATION',
+  LEAVE_CONVERSATION = 'LEAVE_CONVERSATION',
+  SEND_MESSAGE = 'SEND_MESSAGE',
+  STOP_GENERATION = 'STOP_GENERATION',
+
+  // Server -> Client
+  CONVERSATION_JOINED = 'CONVERSATION_JOINED',
+  MESSAGE_ACK = 'MESSAGE_ACK',
+  STREAM_CHUNK = 'STREAM_CHUNK',
+  STREAM_COMPLETE = 'STREAM_COMPLETE',
+  ERROR = 'ERROR',
+}
+
+// Base message interface
+export interface WebSocketMessage<T = unknown> {
+  type: WebSocketEventType;
+  payload: T;
+  timestamp: string;
+  requestId?: string;
+}
+
+// Client -> Server payloads
+export interface JoinConversationPayload {
+  conversationId: string;
+}
+
+export interface LeaveConversationPayload {
+  conversationId: string;
+}
+
+export interface SendMessagePayload {
+  conversationId: string;
+  content: string;
+  streaming?: boolean;
+}
+
+export interface StopGenerationPayload {
+  conversationId: string;
+}
+
+// Server -> Client payloads
+export interface ConversationJoinedPayload {
+  conversationId: string;
+  history: MessageHistoryItem[];
+}
+
+export interface MessageHistoryItem {
+  id: string;
+  role: 'user' | 'assistant' | 'system';
+  content: string;
+  createdAt: string;
+}
+
+export interface MessageAckPayload {
+  messageId: string;
+  status: 'received' | 'processing' | 'error';
+}
+
+export interface StreamChunkPayload {
+  conversationId: string;
+  chunk: string;
+  isComplete: boolean;
+}
+
+export interface StreamCompletePayload {
+  conversationId: string;
+  messageId: string;
+  content: string;
+  tokensUsed?: number;
+  model?: string;
+}
+
+export interface ErrorPayload {
+  code: string;
+  message: string;
+  details?: Record<string, unknown>;
+}

packages/shared/src/websocket/index.ts

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+export * from './events.js';