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/components/layout/shell-config.ts

@@ -0,0 +1,12 @@
+import { appTabs } from '../../router/tabs';
+
+export const shellFrameClassName = 'mx-auto w-full max-w-[1680px] px-8';
+
+export const shellMeta = {
+  productLabel: 'T-Systems Regulation',
+  version: 'v1.0.0',
+  status: 'ONLINE',
+  surface: 'Desktop Web',
+} as const;
+
+export const shellModuleSummary = appTabs.map((tab) => tab.label).join(' / ');