🌐 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>

frontend/app/pages/index.vue

@@ -1,5 +1,14 @@
 <template>
-  <div class="min-h-screen bg-sky-dark flex items-center justify-center">
-    <h1 class="text-4xl font-ui text-sky-text">Skycel</h1>
+  <div class="min-h-screen bg-sky-dark flex flex-col items-center justify-center gap-6">
+    <h1 class="text-4xl font-narrative text-sky-text">{{ $t('landing.title') }}</h1>
+    <p class="text-xl font-ui text-sky-text/70">{{ $t('landing.subtitle') }}</p>
+    <div class="flex gap-4 mt-4">
+      <button class="px-6 py-3 bg-sky-accent text-sky-dark font-ui font-semibold rounded-lg">
+        {{ $t('landing.cta_adventure') }}
+      </button>
+      <button class="px-6 py-3 border border-sky-text/30 text-sky-text font-ui rounded-lg">
+        {{ $t('landing.cta_express') }}
+      </button>
+    </div>
   </div>
 </template>