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/HeaderBrand.tsx

@@ -0,0 +1,19 @@
+import { TLogo } from '../common/TLogo';
+
+export function HeaderBrand() {
+  return (
+    <div className="flex min-w-[280px] shrink-0 items-center gap-4 whitespace-nowrap">
+      <div className="shrink-0">
+        <TLogo size={46} />
+      </div>
+      <div className="flex min-w-0 items-center gap-2 whitespace-nowrap">
+        <span className="text-[1.18rem] font-semibold tracking-[-0.04em] text-foreground">
+          T-Systems
+        </span>
+        <span className="text-[1.02rem] font-light text-muted-foreground">
+          Regulation
+        </span>
+      </div>
+    </div>
+  );
+}