Add agenix-encrypted secrets and flake.lock ...

- Encrypted WireGuard keys for xlab-gateway (wgnet, skyworks, warp)
- Encrypted WireGuard PSK for wg-to-wgnet
- Placeholder skydick WireGuard secret
- Updated disko.nix with correct NVMe disk ID (MEMPEK1J016GAD)
- Generated flake.lock pinning nixpkgs 24.11, disko, agenix, deploy-rs

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