fix: propagate registry_port to container and containerd

[Bisman-Singh]

When using a non-default registry_port (e.g. 5555), the registry container still listened on port 5000 internally. The Docker port mapping (5555:5000) only worked from the host but not from within the Kind network, so pods could not pull images using the configured port.

Root cause:

• docker run -p ${registry_port}:5000 mapped the host port but the container always bound to 5000
• hosts.toml had port 5000 hardcoded instead of using ${registry_port}

Fix:

• Set REGISTRY_HTTP_ADDR=0.0.0.0:${registry_port} so the registry binds on the configured port
• Map the same port on both sides: -p ${registry_port}:${registry_port}
• Use ${registry_port} in hosts.toml instead of hardcoded 5000

Tested with:

• Custom port 5555: pods successfully pull images from kind-registry:5555
• Default port 5000: no regression, works as before

Fixes #143

[Bisman-Singh]

@cpanato could you review this when you have a moment?