🌐 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/Models/Skill.php

@@ -2,12 +2,14 @@
 
 namespace App\Models;
 
+use App\Traits\HasTranslations;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 
 class Skill extends Model
 {
+    use HasTranslations;
     protected $fillable = [
         'slug',
         'name_key',