feat: Add User-Agent header to Allegro API requests

- Implemented buildUserAgent() method in AllegroApiClient, AllegroOAuthClient, and AllegroTrackingService to include User-Agent header in all HTTP requests to Allegro API.
- Updated .env.example to include APP_VERSION and ALLEGRO_USER_AGENT_URL for configuration.
- Created public /info page to provide application details required by Allegro, including app name, version, description, and contact information.
- Added minimalist layout for public pages to ensure a professional appearance.
- Ensured all changes comply with Allegro's API requirements for User-Agent header.

src/Modules/Info/InfoController.php

@@ -0,0 +1,27 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Modules\Info;
+
+use App\Core\Http\Request;
+use App\Core\Http\Response;
+use App\Core\View\Template;
+
+final class InfoController
+{
+    public function __construct(
+        private readonly Template $template
+    ) {
+    }
+
+    public function show(Request $request): Response
+    {
+        $html = $this->template->render('info/allegro', [
+            'title' => 'orderPRO — Informacje o aplikacji',
+            'appName' => (string) (getenv('APP_NAME') ?: 'orderPRO'),
+            'appVersion' => (string) (getenv('APP_VERSION') ?: '1.0.0'),
+        ], 'layouts/public');
+
+        return Response::html($html);
+    }
+}