And every server now has a backup story: export and import

node rssnetwork.js export backup.json writes the whole database -- users, posts, likes, feeds -- into one JSON file and exits without starting the web server; node rssnetwork.js import backup.json loads that file into an empty server. Both work on either engine, which makes the pair the door between them: export from a MySQL server, import into a SQLite one, and the server's whole history comes along -- posts keep their ids, so every permalink survives. The Software versions dialog now names the engine too, so a glance tells you what a server is running on.