feat(deploy): add NixOS live USB ISO for ATM hardware testing

Add NixOS configuration to build a bootable live USB ISO that runs the
ATM Electron app in kiosk mode on physical hardware (UpBoard). The ISO
boots from squashfs, auto-starts X11/openbox, and launches Electron in
production mode.

Key changes:
- deploy/nixos/live.nix: Live USB module (squashfs+tmpfs, no disk install)
- deploy/nixos/flake.nix: Nix flake with ISO build output
- deploy/nixos/provision-atm.sh: Auto-provision LP credentials via API
- deploy/nixos/build-iso.sh: End-to-end build workflow script
- apps/machine: Fix Electron production mode (ELECTRON_FORCE_PROD),
  Vue Router hash mode for file:// protocol, relative asset paths

Build: cd deploy/nixos && bash build-iso.sh
Test:  qemu-system-x86_64 -enable-kvm -m 2G -cdrom result/iso/*.iso

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/machine/src/main.ts

@@ -1,6 +1,6 @@
 import { createApp } from 'vue'
 import { createPinia } from 'pinia'
-import { createRouter, createWebHistory } from 'vue-router'
+import { createRouter, createWebHashHistory } from 'vue-router'
 import App from './App.vue'
 import './style.css'
 
@@ -11,7 +11,7 @@ import CashInView from './views/CashInView.vue'
 
 // Create router
 const router = createRouter({
-  history: createWebHistory(),
+  history: createWebHashHistory(),
   routes: [
     { path: '/', name: 'idle', component: IdleView },
     { path: '/cash-out', name: 'cash-out', component: CashOutView },