Remove the introductionary comments from `query_jobs.sql` and
`query_workers.sql`. Sqlc got confused by this, and placed them in the
wrong (well, not-intended-by-me) place in the generated Go code.
No functional changes.
Convert 'last-rendered' to sqlc. The query is slightly suboptimal.
There's a bug in sqlc: the `ON CONFLICT DO UPDATE` clause is generated
incorrectly. See https://github.com/sqlc-dev/sqlc/issues/3334 for more
info.
This is a bit more work than other queries, as it also breaks apart the
fetching of the job and the worker into separate ones. In other words,
internally the persistence layer API changes.
