Push a container image to a registry with podman push

Documented steps

1. Authenticate first with `podman login REGISTRY` (writes to authfile) or pass one-off creds with `--creds=user:pass`.
2. Push an image from local storage: `podman push [options] image [destination]` (alias of podman image push); default destination transport is `docker`.
3. Push with a specific tag: `podman push myimage quay.io/username/myimage:latest`; the local image name can differ from the target.
4. Set the manifest format with `--format` (oci, v2s2, or v2s1); default compression is gzip (`--compression-format=gzip|zstd|zstd:chunked`, zstd level 1-20 default 3).
5. Capture the resulting digest to a file for reproducible deployment: `podman push --digestfile=/tmp/digest.txt image registry/repo:tag`.
6. Use a specific authfile if your creds are stored elsewhere: `podman push --authfile /path/to/auth.json image registry/repo:tag`.
7. Official docs: https://docs.podman.io/en/latest/markdown/podman-push.1.html