 specify exact image URLs

Please specify exact image URL, because without it, `podman compose up` shows selector menu:

```
f7412d8d8e70aad035cd68405f5195b351dc073b09b44f0578e052a074eb93e7
? Please select an image: 
    registry.fedoraproject.org/postgres:15-alpine
    registry.access.redhat.com/postgres:15-alpine
  ▸ docker.io/library/postgres:15-alpine
    quay.io/postgres:15-alpine
```