What this service stores
Flanner is sold as an operated service, not as a place to keep your work. The lists below describe the database as it is. There is a test in the codebase that fails if a column starts to look like your writing, and another that fails if any page here could render a line of it.
Why it is arranged this way
Devices sync directly with each other, and each change is signed by the machine that wrote it. This service issues short-lived entitlements saying who may read which workspace; the devices check those themselves, offline, without asking us. That is why we can decide access without holding your work, and why a breach here would expose accounts rather than anybody's writing.
It also means we cannot recover anything for you. Your machines hold the only copies, which is the trade being made.