fix(ns-api): handle complex setup networks

Support LAN DHCP, expose logical LAN/WAN interface selection,\nguide WAN static configuration, and strengthen IPv4/CIDR\nvalidation in the console setup helper. Keep keymap changes\nimmediate and avoid rewriting unchanged network state during\nno-op applies.

Assisted-by: OpenCode:openai/gpt-5.4

Author: filippocarletti