[four-random-common-words]

Issue: hashtopolis/server#886
Backend: hashtopolis/server#2502

Adds a Background Jobs page under Config that lists the server's background jobs with type, status, user, timestamps, exit code, message and payload, gated by its own role. Recounting the lines of a file now runs as a background job: the files table reports the recount as queued instead of finished and offers to turn on auto-refresh so the new count shows up. The backend pin and generated API types are updated to the background jobs stack.

[novasam23]

LGTM

Maybe one minor thing, if sorting by either startedAt, finishedAt and exitCode, pagination breaks because these values are nullable and are indeed null in some scenarios.

But I think this is something that should ultimately be fixed in the backend. The backend should be enabled to deal with null values in its OrderFilter.php and PaginationFilter.php. But this is something that can be done later. For now the easiest would be to set isSortable: false for these fields in the frontend.

@s3inlc