Trial database should not be located in a write-protected directory

I made a mistake in Split up the CI pipeline so that the trial arti... (!14 - merged) by installing the SQLite database directly in sites/default, which is write-protected by Drupal. This breaks Drupal entirely.

I think it's okay to put the database at the web root, since this is just a trial anyway, and add a smoke test to the CI pipeline ensuring that the trial is actually working properly.