Step 1 of the build order in docs/decisions.md. Boots, applies migrations
before serving, and serves a health check and an empty admin page.
- 001_init.sql is the full schema from docs/spec.md, including the check
constraints and indexes the old app lacked
- The startup sweep fails submissions left mid-conversion by a restart; an
in-process goroutine dies with the process and those rows would otherwise
say converting forever
- Admin is Basic Auth from env on its own listener, fatal at startup when
ADMIN_PASSWORD is unset
