Expand MinIO storage by adding a server pool with the environment-variable method (MINIO_VOLUMES, requires restart)

Documented steps

1. Verify the new pool's erasure set requirements and parity (EC:M) match the existing cluster using the Erasure Code Calculator.
2. Install MinIO AIStor on the new hardware but do not start it (stop at the environment file review step).
3. Update the cluster topology by appending the new pool to `MINIO_VOLUMES`, including `http[s]://` protocol for EACH pool and keeping all pools at matching protocols. Example: `MINIO_VOLUMES="https://minio-{1...16}.example.net:9000/mnt/drive-{1...16}/minio https://minio-{17...32}.example.net:9000/mnt/drive-{1...16}/minio"`.
4. Apply the updated environment to ALL hosts (existing and new) and validate the contents match across hosts with `shasum`.
5. Initialize the new topology SIMULTANEOUSLY: restart the existing cluster with `mc admin service restart` (restarts all nodes at once) while starting new nodes in parallel with `systemctl start minio`.
6. Monitor with `mc admin info` and `journalctl -u minio`; expect elevated warnings/errors in logs while nodes synchronize.
7. Update load balancers, reverse proxies, and network tools with the new pool hostnames.