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/KeepAliveViewport.tsx

@@ -0,0 +1,45 @@
+import { useEffect, useState } from 'react';
+
+import { appTabs, type AppTabConfig } from '../../router/tabs';
+
+interface KeepAliveViewportProps {
+  activeTab: AppTabConfig;
+}
+
+export function KeepAliveViewport({ activeTab }: KeepAliveViewportProps) {
+  const [mountedTabIds, setMountedTabIds] = useState<string[]>([activeTab.id]);
+
+  useEffect(() => {
+    const timerId = window.setTimeout(() => {
+      setMountedTabIds((prev) => (prev.includes(activeTab.id) ? prev : [...prev, activeTab.id]));
+    }, 0);
+    return () => window.clearTimeout(timerId);
+  }, [activeTab.id]);
+
+  return (
+    <div className="flex min-h-0 flex-1">
+      {appTabs.map((tab) => {
+        const shouldRender = tab.keepAlive ? mountedTabIds.includes(tab.id) : tab.id === activeTab.id;
+        if (!shouldRender) {
+          return null;
+        }
+
+        const TabComponent = tab.component;
+        const isActive = tab.id === activeTab.id;
+
+        return (
+          <div
+            key={tab.id}
+            aria-hidden={!isActive}
+            className={[
+              'min-h-0 flex-1',
+              isActive ? 'flex' : 'hidden',
+            ].join(' ')}
+          >
+            <TabComponent />
+          </div>
+        );
+      })}
+    </div>
+  );
+}