Add @var annotation for geo zone cache property

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Co-authored-by: MaximillianGroup <34328348+MaximillianGroup@users.noreply.github.com>

Author: Copilot

src/services/EnvironmentResolver.php

@@ -45,6 +45,8 @@ final class EnvironmentResolver
 
     /**
      * Memoized geographic trust zone for the current request.
+     *
+     * @var ?string
      */
     private ?string $geoZone = null;