chore: scaffold flake + settings + entry-point quartet

Single-source-of-truth pattern: settings.nix threads identity, host,
and remote topology into every module via specialArgs. configuration.nix
and home.nix stay thin import-lists so module composition is obvious.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

flake.nix

@@ -0,0 +1,67 @@
+{
+  description = "lnbits-sensei — opinionated NixOS scaffold for an LNbits dev stack";
+
+  inputs = {
+    # Pinned to nixos-unstable for fresh LNbits / Lightning tooling.
+    # Bump intentionally; this template does not chase HEAD.
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+
+    home-manager = {
+      url = "github:nix-community/home-manager";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+
+    # Upstream LNbits source. Tracked as a flake input so the lnbits
+    # module can pin to a specific ref and the dev-env helpers can
+    # surface upstream-relative diffs without a separate clone step.
+    #
+    # Override locally with `--override-input lnbits-src path:/your/fork`
+    # when iterating on a feature destined for an upstream PR.
+    lnbits-src = {
+      url = "github:lnbits/lnbits";
+      flake = false;
+    };
+  };
+
+  outputs =
+    {
+      self,
+      nixpkgs,
+      home-manager,
+      ...
+    }@inputs:
+    let
+      system = "x86_64-linux";
+      settings = import ./settings.nix;
+
+      # specialArgs / extraSpecialArgs flow mirrors the omnixy pattern:
+      # `settings` (single source of truth — user, host, identity,
+      # remote topology) is threaded into every NixOS module and into
+      # the home-manager module set, so neither has to re-import it.
+    in
+    {
+      nixosConfigurations.${settings.hostName} = nixpkgs.lib.nixosSystem {
+        inherit system;
+
+        specialArgs = {
+          inherit inputs settings;
+        };
+
+        modules = [
+          ./configuration.nix
+
+          home-manager.nixosModules.home-manager
+          {
+            home-manager = {
+              useGlobalPkgs = true;
+              useUserPackages = true;
+              extraSpecialArgs = {
+                inherit inputs settings;
+              };
+              users.${settings.user} = import ./home.nix;
+            };
+          }
+        ];
+      };
+    };
+}