Update horizon-flake-parts to 0.18.0
Summary
- Update horizon-flake-parts 0.16.0 → 0.18.0
- Adopt named-arg
mkFlakeAPI - Add
ci/nix/ci.nixfor CI partition with horizon-ci + cachix - Remove explicit flakeModule import (auto-imported by mkFlake)
Ref: nix/horizon-flake-parts#7 (closed)