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>

configuration.nix

@@ -0,0 +1,56 @@
+# lnbits-sensei — NixOS entry point.
+#
+# Thin by design. All real config lives in modules/. This file imports
+# the module set and wires per-host settings (hostname, timezone) from
+# the shared `settings` attrset.
+{
+  config,
+  pkgs,
+  lib,
+  settings,
+  ...
+}:
+
+{
+  imports = [
+    # Generated by `nixos-generate-config`. Drop your real
+    # hardware-configuration.nix in alongside this file before the
+    # first build.
+    # ./hardware-configuration.nix
+
+    # Shared helpers (config.lnbits-sensei.lib).
+    ./modules/lib.nix
+
+    # Option schema (lnbits-sensei.*).
+    ./modules/core.nix
+
+    # LNbits service wrapper.
+    ./modules/lnbits.nix
+
+    # Git remote topology — upstream / fork / extras.
+    ./modules/git/remotes.nix
+
+    # Dev environment (worktree mgmt, regtest, fakewallet, tmux).
+    ./modules/dev-env
+  ];
+
+  # --- Per-host settings ---
+
+  lnbits-sensei = {
+    enable = true;
+    user = settings.user;
+    hostName = settings.hostName;
+  };
+
+  networking.hostName = settings.hostName;
+  time.timeZone = settings.timeZone;
+
+  nix.settings.experimental-features = [
+    "nix-command"
+    "flakes"
+  ];
+
+  # Pin the state version that matches the nixpkgs input. Bump
+  # deliberately after reviewing release notes — never auto.
+  system.stateVersion = "24.11";
+}