Limit free storage to 1GB on the SaaS version. When exceeded, card
publishing, comment creation, and JSON card creation are blocked,
and the card footer shows a "self-host Fizzy for unlimited storage"
notice instead of the create buttons. A nearing-limit warning
appears when usage exceeds 500MB.
Uses the same SaaS engine patterns as the removed billing system:
model concern on Account, controller concerns included via
config.to_prepare, view partials in saas/ with Fizzy.saas? guards
in the main app.
Jorge Manrubia