feat: surface API 401 error message with login suggestion in portal generation

Previously, running portal commands while logged out showed the generic
"An unexpected error occurred" message because the SDK's typed 401 error
(UnauthorizedResponseError) was not recognized by the axios-only
handleServiceError. Handle ApiError with status 401 in generatePortal,
extract the API's message, and pair it with a suggestion to run
`apimatic auth login` or pass `--auth-key`.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: MuhammadRafay1

src/infrastructure/service-error.ts

@@ -30,6 +30,14 @@ export class ServiceError {
   static notFound(customMessage: string): ServiceError {
     return new ServiceError(ServiceErrorCode.NotFound, customMessage, {});
   }
+  static unauthorized(apiMessage: string | null): ServiceError {
+    const message = `${apiMessage ?? "You are not authorized to perform this action."} Please run ${f.cmdAlt(
+      "apimatic",
+      "auth",
+      "login"
+    )} to log in, or provide a valid auth key using the ${f.flag("auth-key")} flag.`;
+    return new ServiceError(ServiceErrorCode.UnAuthorized, message, {});
+  }
 
   static readonly values: ServiceError[] = [
     ServiceError.NotFound,

src/infrastructure/services/portal-service.ts

@@ -74,10 +74,16 @@ export class PortalService {
         if (error.statusCode === 400) {
           return err(ServiceError.badRequest(errorMessage, errors));
         }
-        if (error.statusCode === 403) {
-          return err(ServiceError.forbidden(errorMessage));
+        if (error.statusCode === 401) {
+          return err(ServiceError.UnAuthorized);
         }
       }
+      if (error instanceof ApiError && error.statusCode === 401) {
+        // The API reports the reason as {"message": "..."} which the SDK
+        // deserializes into `result` for its typed 401 error.
+        const apiMessage = (error.result as { message?: string } | undefined)?.message ?? null;
+        return err(ServiceError.unauthorized(apiMessage));
+      }
       const serviceError = handleServiceError(error);
       return err(serviceError);
     } finally {