feat: add Hyperspace Pods NixOS module

Create modules/nixos/services/hyperspace.nix for the Hyperspace Pods
P2P AI cluster agent. Registered in flake.nix under lazyworkhorse.

- Fetches CLI binary v5.45.30 via fetchurl with SRI hash verification
- Systemd system service: auto profile, configurable api port 8080,
  ai-worker user, GPU device access (kfd+dri), SupplementaryGroups
  for video+render groups, service hardening
- Firewall: TCP 4001 libp2p, 30301 chain, 8080 API; UDP 4001 libp2p
- AMD MI50 ROCm via HSA_OVERRIDE_GFX_VERSION=9.0.6
- Adds video+render groups to ai-worker for persistent GPU access