Workshop is not compatible with LXD `storage.images_volume`

If LXD is configured to use a dedicated storage volume for images (best practice):

```
$ lxc config show
config:
storage.images_volume: default/images
volatile.uuid: 019e1d67-16a8-768e-b866-92a154ae2842
```

One cannot `workshop launch`:

```
$ cat << EOF > workshop.yaml
name: dev
base: ubuntu@24.04
EOF

$ workshop launch
error: cannot create or load project at "/home/ubuntu": Project feature "features.images" cannot be disabled on projects with storage.project.workshop.ubuntu.images_volume configured
```

To be able to set `features.images`, the [per-project images volume config](https://documentation.ubuntu.com/lxd/latest/reference/release-notes/release-notes-6.6/#per-project-image-and-backup-volumes) needs to be set:

```
$ lxc config set storage.project.workshop.ubuntu.images_volume default/images
$ lxc project set workshop.ubuntu features.images=true
```

However, even with this change, `workshop launch` doesn't work:

```
$ workshop launch
error: cannot perform the following tasks:
- Create new "dev" workshop (Image not provided for instance creation)
"dev" launch aborted
```