Havent used forgejo, but -

Is the zip file a dump of the filesystem / data / config the application needs?

You could want to extract that somewhere, and mount the directory into the container.

https://docs.podman.io/en/latest/markdown/podman-volume-mount.1.html

so for example you extract to /home/forgejo you would map this to a container in podman

Stack to help? https://stackoverflow.com/questions/69298356/how-to-mount-a-volume-from-a-local-machine-on-podman/71576242#71576242