Ensure that database timezone matches IRIS time zone

All travelynx and IRIS timestamps are Europe/Berlin. And the DateTime objects
know that they are Europe/Berlin. However, when inserting into a timestamp with
time zone column, Mojo::Pg or one of the backend DBI/DBD libraries does not
respect the time zone. So, UTC+1 or UTC+2 timestamps are treated as UTC+0,
resulting in major mayhem.