docs: add inline documentation where missing

src/Twig/AppExtension.php

@@ -1,11 +1,20 @@
 <?php
 
+declare(strict_types=1);
+
 namespace App\Twig;
 
 use Twig\Extension\AbstractExtension;
 use Twig\TwigFilter;
 use Twig\TwigFunction;
 
+/**
+ * Twig extension registering booking-related filters and functions.
+ *
+ * Provides filters for formatting (file_size, format_money, format_service_price)
+ * and mapping (map_gender, map_status, map_country, map_nationality), plus
+ * functions for field state checking and participant eligibility.
+ */
 class AppExtension extends AbstractExtension
 {
     public function getFilters(): array

src/Twig/AppRuntime.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace App\Twig;
 
 use App\BusProNet\DataProvider\CountryDataProvider;
@@ -14,6 +16,13 @@ use Twig\Environment;
 use Twig\Extension\RuntimeExtensionInterface;
 use Twig\Extra\Intl\IntlExtension;
 
+/**
+ * Runtime implementation for AppExtension's filters and functions.
+ *
+ * Provides formatting utilities (money, file size, service prices), code-to-label
+ * mapping for display (gender, status, country), and field state introspection
+ * for conditional rendering in templates.
+ */
 class AppRuntime implements RuntimeExtensionInterface
 {
     public function __construct(