docs: gateway optimization & feature-feasibility assessment (2026-06-14) ...

Audit of .1 (R730, healthy) + feasibility of the requested features on the
current network. Key finding: abroad relay RTT 347ms (IPv6 mis-routed via LAX)
vs 65ms (IPv4 direct to Equinix SG) — IPv4 free here, blocked only by Oracle
security list. Plus L3-vs-L7 split, BT/exit QoS (CAKE), DNS-cage, RoCEv2-NFS
(already live), 10G-encrypted, Windows/Android handling. Relay-RTT Grafana panel
added.
Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>