🌐 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/components/ui/LanguageSwitcher.vue

@@ -0,0 +1,22 @@
+<template>
+  <div class="flex items-center gap-1" role="group" :aria-label="$t('common.language')">
+    <button
+      v-for="loc in availableLocales"
+      :key="loc.code"
+      :aria-current="currentLocale === loc.code ? 'true' : undefined"
+      :class="[
+        'px-2 py-1 text-sm font-ui rounded transition-colors',
+        currentLocale === loc.code
+          ? 'text-sky-accent font-semibold'
+          : 'text-sky-text/50 hover:text-sky-text',
+      ]"
+      @click="switchLocale(loc.code)"
+    >
+      {{ loc.code.toUpperCase() }}
+    </button>
+  </div>
+</template>
+
+<script setup lang="ts">
+const { currentLocale, availableLocales, switchLocale } = useLocale()
+</script>