deploy-rs: update xlab-gateway hostname, add NOPASSWD sudo ...

- Change xlab-gateway deploy hostname to WAN IP (166.111.98.29)
- Add NOPASSWD sudo rules for deploy-rs activation commands
  (nix-env, activate scripts)

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Initial skyworks infrastructure flake ...

Unified NixOS configuration for skydick (storage server) and
xlab-gateway (lab router). Flat module structure with shared
common/users/ssh modules, agenix secrets, disko, and deploy-rs.

Co-Authored-By: Claude Opus 4.6 <[email protected]>