[ 🌠 Feat ] Let backends return (signed) links instead of images

[freswa]

Is your feature request related to a problem? Please describe.
To reduce load on the lust server, I'd like to serve pictures directly from block storage.

Describe the solution you'd like
When the block storage is public, a static link should be returned instead of the image itself. If the block storage is private a signed link should be returned instead.

Describe alternatives you've considered
Only other solutions that are more complicated e.g. imageflow.