v0.1.30-pre.75

preview: nothing a person can see changes in this one. app-core's jvm tests now open their
databases on files as every host does, 28 sites in 24 files, and the build check that refuses
a new in-memory one covers that module as well as ui from here on. Two sites stay on the
allowlist with their reasons written on the line.

No migration: schema stays at 22 as at pre.74, so an account this build opens still needs
pre.61 or newer. Going back below that drops you at the account picker as though the account
were gone.

Landed from pr-kettle, pull request bc72d8a5 at tip 561eafdf, merge 49ff9e85. The app-core half
of #47fcbf7a, which stays open for cordn-sync and conformance.