fix(back-end): fix 3mf calculator

frontend/src/app/features/calculator/calculator-page.component.scss

@@ -9,6 +9,12 @@
   margin: 0 auto;
 }
 
+.error-action {
+  display: flex;
+  justify-content: center;
+  margin-top: calc(var(--space-4) * -1);
+}
+
 .content-grid {
   display: grid;
   grid-template-columns: 1fr;
@@ -82,6 +88,15 @@
   line-height: 2;
 }
 
+.zero-result-card p {
+  color: var(--color-text-muted);
+  line-height: 1.6;
+}
+
+.zero-result-action {
+  margin-top: var(--space-4);
+}
+
 .loader-content {
   text-align: center;
   max-width: 300px;