Always show a banner for the trash location

Currently, we only show an info bar in the trash when trash pruning is enabled. I think that it makes sense to always show a banner in the trash, in order to communicate that it's a special location.

I think that we can also improve the wording of the banner: the "Items in the trash older than 30 days are automatically deleted" is a bit awkward and long.

Design suggestion:

The idea here is to make manual emptying accessible when automatic pruning is off, since that's when it's mainly needed.