Class HTTPError

frontend/src/shared/lib/errors.ts:127–291

 * - 5xx (server errors): Retry 3 times - server might recover
 */
export class HTTPError extends AppError {
  readonly maxRetries: number

  constructor(config: AppErrorConfig) {
    super(config)

    // 5xx errors are retryable (server might recover)
    // 4xx errors are not retryable (client error - permanent)
    this.maxRetries = this.isRetryable ? 3 : 0
  }

  /**
   * Create HTTPError from fetch Response
   */
  static async fromResponse(response: Response, endpoint: string): Promise<HTTPError> {
    const status = response.status
    const config = HTTPError.getErrorConfig(status)
    const isDevelopment = process.env.NODE_ENV === 'development'

    // Try to extract error details from response body
    let responseBody: unknown
    try {
      responseBody = await response.json()
    } catch {
      // Response body is not JSON - ignore
    }
    let serverMessage =
      typeof (responseBody as any)?.error === 'string' ? (responseBody as any).error :
      typeof (responseBody as any)?.message === 'string' ? (responseBody as any).message :
      typeof (responseBody as any)?.detail === 'string' ? (responseBody as any).detail :
      ''
    try {
      serverMessage = JSON.parse(serverMessage)?.error || serverMessage
    } catch {}

    return new HTTPError({
      ...config,
      message: serverMessage || config.message,
      userMessage: serverMessage || config.userMessage,
      statusCode: status,
      technicalDetails: isDevelopment
        ? {
            status,
            statusText: response.statusText,
            ...(responseBody ? { response: JSON.stringify(responseBody).slice(0, 200) } : {}),
          }
        : undefined,
    })
  }

  /**
   * Map HTTP status codes to error configurations
   * Following industry-standard error messages
   */
  private static getErrorConfig(status: number): Omit<AppErrorConfig, 'statusCode' | 'technicalDetails'> {
    // 4xx Client Errors (permanent - no retry)
    if (status === 400) {
      return {