Implement localization for API responses and error messages

- Added localization support for API responses in English and Spanish.
- Introduced a middleware to set the API locale based on the Accept-Language header.
- Updated various exception messages and validation responses to use localized strings.
- Created new language files for English and Spanish translations.
- Refactored existing code to replace hardcoded messages with localized strings.
- Added tests to verify localization functionality and response correctness.

app/Domains/MailTest/Services/MailTestService.php

@@ -24,7 +24,8 @@ class MailTestService
         );
 
         return [
-            'message' => 'Correo de prueba enviado correctamente.',
+            'code' => 'mail.test_sent',
+            'message' => __('api.mail.test_sent'),
             'recipient' => $recipient,
             'tenant_code' => $tenant->codigo,
             'mailer' => $mailService->mailerName(),