feat: implement new layout components and routing structure

- Added HeaderLayout component for the application header.
- Introduced KeepAliveViewport for managing tab states and rendering.
- Created TabNav for tab navigation with animated indicator.
- Removed old Tabs component in favor of new layout structure.
- Updated routing with AppRouter and defined appTabs for navigation.
- Enhanced theme context to manage dark mode styles.
- Added new UI components: Badge, Button, Separator, and Tabs.
- Refactored pages to utilize new layout components and improve responsiveness.
- Updated global styles for better theming and layout consistency.
- Introduced TypeScript path aliases for cleaner imports.

frontend/src/contexts/ThemeContext.tsx

@@ -16,13 +16,14 @@ export const ThemeProvider: React.FC<ThemeProviderProps> = ({ children }) => {
   };
 
   useEffect(() => {
+    document.documentElement.classList.toggle('dark', isDark);
+    document.body.classList.toggle('dark-mode', isDark);
+
     if (isDark) {
-      document.documentElement.classList.add('dark');
       document.body.style.background = '#0a0a12';
       return;
     }
 
-    document.documentElement.classList.remove('dark');
     document.body.style.background = '#ffffff';
   }, [isDark]);