fix(t231): expose freight preflight errors

backend-api/internal/transport/httpapi/admin_handlers.go

@@ -845,6 +845,18 @@ func writeUsecaseError(ctx *gin.Context, err error) {
 	case usecase.ErrorKindUnavailable:
 		status = http.StatusServiceUnavailable
 	}
+	switch typed.Code {
+	case "ERP_NOT_CONFIGURED", "ERP_LOGIN_REJECTED":
+		status = http.StatusUnprocessableEntity
+	case "ERP_RESPONSE_INVALID":
+		status = http.StatusBadGateway
+	case "OCR_SERVICE_INVALID", "ERP_UNAVAILABLE":
+		status = http.StatusServiceUnavailable
+	}
+	message := typed.Message
+	if preflightMessage, ok := freightPreflightPublicMessage(typed.Code); ok {
+		message = preflightMessage
+	}
 	details := gin.H{}
 	if len(typed.Fields) > 0 {
 		details["fields"] = typed.Fields
@@ -853,12 +865,29 @@ func writeUsecaseError(ctx *gin.Context, err error) {
 		ctx,
 		status,
 		typed.Code,
-		typed.Message,
+		message,
 		typed.Retryable,
 		details,
 	)
 }
 
+func freightPreflightPublicMessage(code string) (string, bool) {
+	switch code {
+	case "ERP_NOT_CONFIGURED":
+		return "ERP credentials are not configured", true
+	case "ERP_LOGIN_REJECTED":
+		return "ERP login was rejected", true
+	case "ERP_RESPONSE_INVALID":
+		return "ERP response is invalid", true
+	case "OCR_SERVICE_INVALID":
+		return "OCR service is invalid", true
+	case "ERP_UNAVAILABLE":
+		return "ERP is temporarily unavailable", true
+	default:
+		return "", false
+	}
+}
+
 func writePublicError(
 	ctx *gin.Context,
 	status int,