are pg_cron and pgaudit database specific extensions? or is one installation per server enough?

I'm quite versed in postgresql, but new to any extension other than postgis. for example, one of the first things I do when setting up an instance is to install postgis in template1, so it's available in every db I create (most of them handle geospatial data). I'd like something similar for pg_cron and pgaudit, but I'm not sure it's required. are these extensions "one per cluster" or do they need installing in each separate database? I believe pgaudit is per server, as it records everything, but confirmation would be helpful. pg_cron I'm not so sure about. thanks all!