Publish nixica-ci via importAndPublish for downstream reuse

Summary

• Move nixica-ci from dev/nix/modules/flake/ to nix/modules/flake/ using importAndPublish
• Published as self.modules.flake.nixica-ci for downstream consumers
• Partition inherits the module via extendModules, no explicit import needed in partition context
• Test fixtures import it via inputs.nixica.modules.flake.nixica-ci in devModules

Consumer usage:

{ inputs, ... }: {
  imports = [ inputs.nixica.modules.flake.nixica-ci ];
  nixica.ci.leaf.enable = true;
}

Closes #16 (closed)