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.yml

@@ -51,8 +51,6 @@ services:
       NUXT_STRAPI_URL: ${STRAPI_URL}
       NUXT_PUBLIC_SITE_URL: ${PUBLIC_SITE_URL}
       NUXT_PUBLIC_STRAPI_URL: ${PUBLIC_STRAPI_URL}
-      # Absolute origin for the alternate-language links.
-      NUXT_PUBLIC_I18N_BASE_URL: ${PUBLIC_SITE_URL}
 
   caddy:
     image: caddy:2-alpine