Run tests through dockerized Postgres wrapper

[meoyawn]

setting up a foundation for agentic solving of #99

addressing #107 (review)

prompt:

- `make test` uses wrapper described in https://michael.stapelberg.ch/posts/2024-11-19-testing-with-go-and-postgresql-ephemeral-dbs/ . wrapper is already present in `internal/pgdocker`, needs minimal changes
- no `*.sql` is changed
- in Makefile only `test` target is changed
- `make lint` passes
- `make update-acceptance-test` passes (should not update anything because no `*.sql` is changed)
- `make test` passes