Add comprehensive performance monitoring and testing infrastructure

- Implement performance dashboard with real-time metrics tracking
- Add React hooks for smart polling, debouncing, and active source lookup
- Create Jest testing framework with comprehensive test suites for components, API endpoints, and utilities
- Enhance UI components with optimized rendering and memoization
- Improve polling efficiency with visibility detection and adaptive intervals

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

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

app/layout.tsx

@@ -2,6 +2,7 @@ import './globals.css';
 import Header from '@/components/Header';
 import Footer from '@/components/Footer';
 import { ErrorBoundary } from '@/components/ErrorBoundary';
+import PerformanceDashboard from '@/components/PerformanceDashboard';
 
 export const metadata = {
   title: 'OBS Source Switcher',
@@ -19,6 +20,7 @@ export default function RootLayout({ children }: { children: React.ReactNode })
           </ErrorBoundary>
         </main>
         <Footer />
+        <PerformanceDashboard />
       </body>
     </html>
   );