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/Http/Middleware/SetApiLocale.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use Closure;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\App;
+use Symfony\Component\HttpFoundation\Response;
+
+class SetApiLocale
+{
+    public function handle(Request $request, Closure $next): Response
+    {
+        if (! $request->is('api/*')) {
+            return $next($request);
+        }
+
+        $supportedLocales = config('app.supported_locales', ['es', 'en']);
+        $acceptLanguage = $request->header('Accept-Language');
+        $locale = is_string($acceptLanguage) && $acceptLanguage !== ''
+            ? $request->getPreferredLanguage($supportedLocales)
+            : null;
+        $locale ??= config('app.locale', 'es');
+
+        App::setLocale($locale);
+
+        $response = $next($request);
+        $response->headers->set('Content-Language', $locale);
+        $response->setVary('Accept-Language', false);
+
+        return $response;
+    }
+}