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/falukant/MessagesDialog.vue

@@ -821,7 +821,7 @@ export default {
 }
 
 .messages > li .footer {
-  color: #f9a22c;
+  color: #FF6B35;
   font-size: 0.8em;
   margin-top: 0.3em;
   display: flex;