Remove i18n, keep only Italian and rely on browser translation

The interface was translated in en/it/es/fr via @nuxtjs/i18n. Drop the
module, the locale files, and the language switcher: the UI is now
static Italian text, with translation for foreign visitors left to the
Google Translate browser extension instead of the app.

docker-compose.dev.yml

@@ -16,4 +16,3 @@ services:
     environment:
       NUXT_PUBLIC_SITE_URL: http://localhost:3000
       NUXT_PUBLIC_STRAPI_URL: http://localhost:1337
-      NUXT_PUBLIC_I18N_BASE_URL: http://localhost:3000