Initial NixOS infra flake skeleton

flake.nix

@@ -0,0 +1,53 @@
+{
+  description = "Flowback infra (NixOS): Nextcloud + Forgejo, staging + production";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+
+    # Optional, but strongly recommended for secrets:
+    sops-nix.url = "github:Mic92/sops-nix";
+    sops-nix.inputs.nixpkgs.follows = "nixpkgs";
+  };
+
+  outputs = { self, nixpkgs, sops-nix, ... }:
+  let
+    mkHost = { name, system, modules }:
+      nixpkgs.lib.nixosSystem {
+        inherit system;
+        modules =
+          modules ++ [
+            sops-nix.nixosModules.sops
+          ];
+        specialArgs = { inherit name; };
+      };
+  in
+  {
+    # Staging host (x86_64 for VM/cloud)
+    nixosConfigurations.staging = mkHost {
+      name = "staging";
+      system = "x86_64-linux";
+      modules = [
+        ./hosts/staging/configuration.nix
+      ];
+    };
+
+    # Production host (x86_64 for VM/cloud)
+    nixosConfigurations.production = mkHost {
+      name = "production";
+      system = "x86_64-linux";
+      modules = [
+        ./hosts/production/configuration.nix
+      ];
+    };
+
+    # Raspberry Pi example (aarch64) — use when you’re ready
+    # nixosConfigurations.rpi-staging = mkHost {
+    #   name = "rpi-staging";
+    #   system = "aarch64-linux";
+    #   modules = [
+    #     ./hosts/staging/configuration.nix
+    #     ./hosts/staging/rpi-hardware.nix
+    #   ];
+    # };
+  };
+}