Static IP registration under NSE/INVG/67858: secondary IP, weekly change limit, and IPv6 support

A few specifics that trip people up on this, all of them from NSE/INVG/67858 (5 May 2025): You register a static IP with the broker, and you can register a secondary for redundancy. That second part is the one people miss and it is the intended answer to failover. Mapped addresses can be updated at most once per calendar week.