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.

tests/Feature/Localization/ApiLocalizationTest.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace Tests\Feature\Localization;
+
+use Tests\TestCase;
+
+class ApiLocalizationTest extends TestCase
+{
+    public function test_it_negotiates_spanish_from_accept_language(): void
+    {
+        $this->withHeader('Accept-Language', 'es-AR,es;q=0.9')
+            ->postJson('/api/login')
+            ->assertUnprocessable()
+            ->assertHeader('Content-Language', 'es')
+            ->assertJsonPath('errors.email.0', 'El campo email es obligatorio.')
+            ->assertJsonPath('errors.password.0', 'El campo contraseña es obligatorio.');
+    }
+
+    public function test_it_negotiates_english_from_accept_language(): void
+    {
+        $this->withHeader('Accept-Language', 'en-US,en;q=0.9')
+            ->postJson('/api/login')
+            ->assertUnprocessable()
+            ->assertHeader('Content-Language', 'en')
+            ->assertJsonPath('errors.email.0', 'The email field is required.')
+            ->assertJsonPath('errors.password.0', 'The password field is required.');
+    }
+
+    public function test_it_localizes_framework_error_responses(): void
+    {
+        $this->withHeader('Accept-Language', 'en')
+            ->getJson('/api/route-that-does-not-exist')
+            ->assertNotFound()
+            ->assertHeader('Content-Language', 'en')
+            ->assertJson([
+                'code' => 'errors.not_found',
+                'message' => 'The requested resource was not found.',
+            ]);
+    }
+}