🌐 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/composables/useApi.ts

@@ -0,0 +1,18 @@
+export const useApi = () => {
+  const config = useRuntimeConfig()
+  const { locale } = useI18n()
+
+  const apiFetch = async <T>(endpoint: string, options: Record<string, any> = {}) => {
+    return await $fetch<T>(`${config.public.apiUrl}${endpoint}`, {
+      ...options,
+      headers: {
+        'X-API-Key': config.public.apiKey as string,
+        'Accept-Language': locale.value,
+        'Content-Type': 'application/json',
+        ...options.headers,
+      },
+    })
+  }
+
+  return { apiFetch }
+}