🌐 Add full i18n system frontend + API (Story 1.3)

Nuxt i18n with lazy-loaded JSON files, localized routes, hreflang SEO tags,
LanguageSwitcher component. Laravel SetLocale middleware, HasTranslations trait,
API Resources and Controllers for projects/skills with Accept-Language support.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

api/app/Traits/HasTranslations.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace App\Traits;
+
+use App\Models\Translation;
+
+trait HasTranslations
+{
+    public function getTranslated(string $keyField, ?string $lang = null): ?string
+    {
+        $lang = $lang ?? request()->attributes->get('locale', 'fr');
+        $key = $this->{$keyField};
+
+        if (!$key) {
+            return null;
+        }
+
+        return Translation::getTranslation($key, $lang);
+    }
+}