Clean up, rearrange and add comments in flake.nix

I could in theory just import all flake files from particular host, but so far
there aren't a lot of files in there, and I like the explicitness, and central
point of entry in flake.nix

Not sure what went wrong the last time I tried it. This seems to be working, so
I'll keep it and keep an eye for a while

flake.nix

@@ -26,22 +26,33 @@
       enterprise = nixpkgs.lib.nixosSystem {
         system = "x86_64-linux";
         modules = [
-          ./hosts/enterprise/configuration.nix
-          ./modules/agenix.nix
-          agenix.nixosModules.age
-          (import ./nix.nix)
-          (import ./hosts/enterprise/sound.nix)
-          (import ./hosts/enterprise/fish.nix)
-          (import ./hosts/enterprise/backup.nix)
-          (import ./hosts/enterprise/nvidia.nix)
-          (import ./cachix.nix)
+
+          # Overlays
           { nixpkgs.overlays = [ emacs-overlay.overlay ]; }
+
+          # Common
+          ./nix.nix
+          ./cachix.nix
+
+          # Modules and module config
+          agenix.nixosModules.age
+          ./modules/agenix.nix
+
+          # Host-specific config
+          ./hosts/enterprise/sound.nix
+          ./hosts/enterprise/fish.nix
+          ./hosts/enterprise/backup.nix
+          ./hosts/enterprise/nvidia.nix
+          ./hosts/enterprise/configuration.nix
+
+          # User-specific config : Home-manager
           home-manager.nixosModules.home-manager
           {
             home-manager.useGlobalPkgs = true;
             home-manager.useUserPackages = true;
             home-manager.users.payas = import ./hosts/enterprise/home.nix;
           }
+
         ];
       };
     };