The only solution is to have these files locally on the server and then use an external bind mount.
I solved this in my docker-compose-gitops-action by just inserting secrets before copying the files to the server.
https://fariszr.com/docker-compose-gitops-github/
you can't do that with dokploy even with this dokploy action so it's triggers a pull from the source repo only.
Also the preview feature on dokploy is almost useless because there is no variable to get the preview URL dynamically.
Just mount it at the same path on all hosts and then bind-mount it into the container and it will work no matter where the container is scheduled
Have to think about backup strategy yourself tho.
If you don't, it's going to be accessible via :3000 AND whatever domain you choose over https:// (provided it can use let's encrypt cert). So it's a bit of a gotcha.