UwULock Server 0.0.1

The foundation. UwULock Server runs, updates itself safely and backs itself up — but it does
not keep a vault yet. Accounts, sync and everything the Bitwarden apps need come in 0.1; the
whole way is in docs/plan.md.

• One container, set up by install.sh. It asks one thing: whether the server gets its own
  certificate from Let's Encrypt, or runs behind a reverse proxy you already have. The official
  Bitwarden apps need a certificate the system trusts, so there is no self-made one.
• Let's Encrypt built in, over port 443 alone (TLS-ALPN-01), renewed by the server itself.
  Or your own certificate files, read again when they change.
• update.sh with the channels latest, beta and edge: a backup first, then the new version,
  and the old one back if the new one does not come up.
• Backups every night and before every update, seven kept, never at the cost of a full disk;
  uwulock-server restore puts one back.
• /alive, /api/alive and /api/now like Bitwarden's server, and /healthz for the
  container's health check.
• Measured against Vaultwarden from the start: uwulock-bench and a weekly run in CI. The
  first numbers are in docs/performance.md.