Calculates IPv4/IPv6 subnet details from CIDR notation — network/broadcast, netmask, wildcard (Cisco ACL) mask, binary/hex masks, usable host range, RFC classification (private/loopback/multicast), supernet, and subnet-split counts. Pass comma-separated CIDRs to detect overlaps and classify each pair (subnet/supernet/partial overlap/disjoint); multi-CIDR responses return {subnets, overlaps}.