fix!: make all nixosConfigurations build

Specifically `homix`
- remove manual `home-manager` module definition
Import `(r)agenix` and `agenix-rekey` by default for all `NixOS` configurations
Move `machines.nix` flake module import to `configuration.nix` from `flake.nix`

machines/nixos/x86_64-linux/jeeves/configuration.nix

@@ -4,8 +4,6 @@
     inputs.hardware.nixosModules.common-cpu-amd
     inputs.hardware.nixosModules.common-gpu-amd
     ./disko.nix
-    inputs.ragenix.nixosModules.default
-    inputs.agenix-rekey.nixosModules.default
     ./network.nix
     ./wireguard.nix
     ./nginx.nix