feat: inject ThemeService into App component and enhance responsive styles for navigation items

frontend/src/styles.scss

@@ -272,6 +272,29 @@
 }
 
 @layer blocks {
+  @media (max-width: 959px) {
+    .navigation-item .mdc-button__label {
+      display: flex;
+      width: 100%;
+      height: 100%;
+      min-width: 0;
+      flex-direction: column;
+      align-items: center;
+      justify-content: center;
+    }
+
+    .navigation-item .mdc-button__label > span {
+      display: block;
+      width: 100%;
+      min-width: 0;
+      overflow-wrap: break-word;
+      font-size: 0.62rem;
+      line-height: 1.05;
+      text-align: center;
+      white-space: normal;
+    }
+  }
+
   .busy-fieldset {
     min-width: 0;
     margin: 0;