chore: separate backend from frontend

flake.nix

@@ -1,7 +1,6 @@
 {
   inputs = {
     nixpkgs.url = "github:cachix/devenv-nixpkgs/rolling";
-    systems.url = "github:nix-systems/default";
     alejandra = {
       url = "github:kamadorueda/alejandra/4.0.0";
       inputs.nixpkgs.follows = "nixpkgs";
@@ -14,6 +13,10 @@
       url = "github:oxalica/rust-overlay";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+    devenv-root = {
+      url = "file+file:///dev/null";
+      flake = false;
+    };
   };
 
   nixConfig = {
@@ -30,27 +33,26 @@
   outputs = {
     self,
     nixpkgs,
-    devenv,
-    systems,
+    flake-utils,
     rust-overlay,
     alejandra,
     ...
-  } @ inputs: let
-    forEachSystem = nixpkgs.lib.genAttrs (import systems);
-  in {
-    formatter = forEachSystem (system: alejandra.defaultPackage.${system});
-    packages = forEachSystem (system: import ./backend/nix/package.nix { inherit rust-overlay inputs system; });
-    devShells = forEachSystem (
+  } @ inputs:
+    flake-utils.lib.eachDefaultSystem (
       system: let
-        pkgs = nixpkgs.legacyPackages.${system};
-      in {
-        backend = import ./backend/nix/shell.nix {
-          inherit inputs pkgs system self rust-overlay;
+        overlays = [(import rust-overlay)];
+        pkgs = import nixpkgs {inherit system overlays;};
+        rustVersion = pkgs.rust-bin.stable.latest.default;
+        rustPlatform = pkgs.makeRustPlatform {
+          cargo = rustVersion;
+          rustc = rustVersion;
         };
-        frontend = import ./frontend/shell.nix {
-          inherit inputs pkgs self;
+      in {
+        formatter = alejandra.defaultPackage.${system};
+        packages = import ./nix/package.nix {inherit pkgs rustPlatform;};
+        devShell = import ./nix/shell.nix {
+          inherit inputs pkgs self rustVersion;
         };
       }
     );
-  };
 }