feat: support VITE_FORCE_MOCK for demo/dev environments

When VITE_FORCE_MOCK=true, initialize with mock services directly
instead of requiring Electron or a live Lightning.Pub connection.

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

apps/machine/src/App.vue

@@ -29,6 +29,8 @@ onMounted(async () => {
   try {
     if (isElectron) {
       await atmStore.initializeForProduction()
+    } else if (import.meta.env.VITE_FORCE_MOCK === 'true') {
+      atmStore.initialize()
     } else {
       await atmStore.initializeWithLightning()
     }