feat: add fund-atm CLI for generating ATM funding invoices

Standalone Node.js script that generates a Lightning invoice for
the ATM's Lightning.Pub account. Reads config from .env, connects
to the relay, creates an invoice via Nostr RPC, displays a QR code
in the terminal, and prints the BOLT11.

Bundled as self-contained CJS with esbuild (all dependencies inlined)
so it works from the nix store without separate node_modules.

Usage: fund-atm <amount_sats>
  e.g. fund-atm 100000
       fund-atm 100000 sats

Added to NixOS systemPackages for both live and installed configs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

flake.nix

@@ -78,7 +78,14 @@
           modules = [
             ./deploy/nixos/live.nix
             determinate.nixosModules.default
-            { environment.systemPackages = [ atm-tui.packages.${system}.default ]; }
+            {
+              environment.systemPackages = [
+                atm-tui.packages.${system}.default
+                (pkgs.writeShellScriptBin "fund-atm" ''
+                  exec ${pkgs-unstable.nodejs}/bin/node ${atm-app}/dist-electron/fund-atm.bundle.cjs "$@"
+                '')
+              ];
+            }
           ];
         };
 
@@ -109,8 +116,13 @@
                 appDir = "${atm-app}";
               };
 
-              # Operator TUI for local machine management
-              environment.systemPackages = [ atm-tui.packages.${system}.default ];
+              # Operator TUI and CLI tools
+              environment.systemPackages = [
+                atm-tui.packages.${system}.default
+                (pkgs.writeShellScriptBin "fund-atm" ''
+                  exec ${pkgs-unstable.nodejs}/bin/node ${atm-app}/dist-electron/fund-atm.bundle.cjs "$@"
+                '')
+              ];
 
               # Electron sandbox needs unprivileged user namespaces
               boot.kernel.sysctl."kernel.unprivileged_userns_clone" = 1;