feat(layout): implement responsive layout system with navigation

- Add comprehensive layout system (AppLayout, Header, Sidebar, MainContainer)
- Implement responsive navigation with mobile-friendly collapsing sidebar
- Add theme toggle component with smooth transitions
- Include proper ARIA labels and keyboard navigation
- Support authentication state in navigation

Layout system provides consistent structure across all pages with
theme-aware styling and accessibility compliance.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

reactrebuild0825/src/components/layout/index.ts

@@ -0,0 +1,5 @@
+// Layout component exports
+export { AppLayout, type AppLayoutProps } from './AppLayout';
+export { Header, type HeaderProps } from './Header';
+export { Sidebar, type SidebarProps } from './Sidebar';
+export { MainContainer, type MainContainerProps } from './MainContainer';