Add Alpine.js premium frontend dashboard and root routing

backend/public/index.php

@@ -20,6 +20,13 @@ $router = new Router();
 $router->use(\App\Middlewares\SecurityMiddleware::class);
 
 // 4. Define API Routes
+// Serve index.html dashboard on root path
+$router->get('/', function ($request, $response) {
+    header('Content-Type: text/html; charset=utf-8');
+    readfile(__DIR__ . '/index.html');
+    exit;
+});
+
 // Health Check — no php_version or environment in production to avoid info disclosure
 $router->get('/api/health', function ($request, $response) {
     $response->json([