Make createModelForPlatform method static

- Change createModelForPlatform from instance to static method
- Update method call to use self::createModelForPlatform()
- Method doesn't use any instance properties, so static is more appropriate

Author: OskarStark

src/ai-bundle/src/Command/PlatformInvokeCommand.php

@@ -104,7 +104,7 @@ protected function initialize(InputInterface $input, OutputInterface $output): v
             throw new InvalidArgumentException('Model is required.');
         }
 
-        $this->model = $this->createModelForPlatform($platformName, $modelName);
+        $this->model = self::createModelForPlatform($platformName, $modelName);
 
         $this->message = trim((string) $input->getArgument('message'));
 
@@ -148,7 +148,7 @@ protected function execute(InputInterface $input, OutputInterface $output): int
         return Command::SUCCESS;
     }
 
-    private function createModelForPlatform(string $platformName, string $modelName): Model
+    private static function createModelForPlatform(string $platformName, string $modelName): Model
     {
         return match ($platformName) {
             'openai' => new \Symfony\AI\Platform\Bridge\OpenAi\Gpt($modelName),