feat(app): add FrankenPHP worker script for Symfony

Boot the Symfony kernel once at startup, then loop with
frankenphp_handle_request() to handle every incoming request without
re-bootstrapping the framework. Supports MAX_REQUESTS env var for
graceful worker restarts.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/worker.php

@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+use App\Kernel;
+use Symfony\Component\HttpFoundation\Request;
+
+require_once dirname(__DIR__).'/vendor/autoload.php';
+
+$kernel = new Kernel($_SERVER['APP_ENV'] ?? 'prod', (bool) ($_SERVER['APP_DEBUG'] ?? false));
+$kernel->boot();
+
+$handler = static function () use ($kernel): void {
+    $request = Request::createFromGlobals();
+    $response = $kernel->handle($request);
+    $response->send();
+    $kernel->terminate($request, $response);
+};
+
+$maxRequests = (int) ($_SERVER['MAX_REQUESTS'] ?? 0);
+$requestCount = 0;
+
+while (\frankenphp_handle_request($handler)) {
+    if ($maxRequests > 0 && ++$requestCount >= $maxRequests) {
+        break;
+    }
+}
+
+$kernel->shutdown();