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.

.env.example

@@ -1,4 +1,5 @@
 APP_NAME=orderPRO
+APP_VERSION=1.0.0
 APP_ENV=local
 APP_DEBUG=true
 APP_URL=http://localhost:8000
@@ -23,3 +24,7 @@ DB_CHARSET=utf8mb4
 # Windows XAMPP: C:/xampp/php/extras/ssl/cacert.pem
 # Linux: /etc/ssl/certs/ca-certificates.crt
 CURL_CA_BUNDLE_PATH=
+
+# Allegro User-Agent — wymagany od 01.07.2026 (art. 3.4.c Regulaminu REST API)
+# Format: {APP_NAME}/{APP_VERSION} (+{ALLEGRO_USER_AGENT_URL})
+ALLEGRO_USER_AGENT_URL=https://orderpro.pl/info