Update color palette and styles across components for improved visual consistency

- Changed theme color in index.html to a brighter orange for better aesthetics.
- Introduced a modern color palette in styles.scss for enhanced readability and consistency.
- Updated various components (AppFooter, AppNavigation, DialogWidget, etc.) to utilize new color variables, ensuring a cohesive look throughout the application.
- Adjusted button styles and hover effects for improved user interaction feedback.
- Enhanced background colors and text colors for better contrast and visibility.

frontend/src/components/SimpleTabs.vue

@@ -57,7 +57,7 @@ export default {
 }
 
 .simple-tab.active {
-  background: #F9A22C;
+  background: #FF6B35;
   color: #000;
 }
 </style>