Add int return type to NodesValidatorCommand::execute()

[itaymesh]

Symfony Console's Command::execute() declares an int return type, but the override in NodesValidatorCommand lacked the type hint, causing a signature mismatch.

Change

• Console/Command/NodesValidatorCommand.php: add : int return type to execute()

-    public function execute(InputInterface $input, OutputInterface $output)
+    public function execute(InputInterface $input, OutputInterface $output): int

The method body already returns 0 in all paths; no logic changes were needed.