perf: ⚡ Cambiata funzione in modo da essere più performante

Motivo: Inspection EA Ultimate e [is_file or file_exists in PHP](https://stackoverflow.com/a/792909)

app/Http/Middleware/HandleInertiaRequests.php

@@ -38,7 +38,7 @@ class HandleInertiaRequests extends Middleware
             'locale' => fn () => app()->getLocale(),
             'translations' => function () {
                 $json = resource_path('lang/'.app()->getLocale().'.json');
-                if (!file_exists($json)) {
+                if (!is_file($json)) {
                     return [];
                 }