Mailman3 and Website-V2

https://cppalliance.org/sam/2025/07/10/SamsQ2Update.html

Mailman 3 replaced Mailman 2 for Boost mailing lists, adding archive import, Redis cache and faster posting; Boost.org V2 was launched with DNS switch, IPv6, autoscaling, CDN tweaks, doc‑page caching and updates to Antora, CI defaults, monitoring and runner upgrades.