feat(electron): add persistent auth, auto-updater, and NAS copy script

- Integrate electron-store for persistent PocketBase auth backup
  across localStorage clears and app reinstalls
- Switch build target from portable to nsis to generate latest.yml
  for electron-updater generic provider
- Add user confirmation dialogs before download and before install
- Add post-build script to copy .exe/.yml/.nupkg to NAS share and
  local electron-update/ directory for nginx volume mount
- Mount ./electron-update into frontend nginx containers via
  docker-compose for automatic update file serving

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

docker-compose.uat.yml

@@ -59,6 +59,8 @@ services:
     container_name: gamegroup-frontend-uat
     ports:
       - "7034:80"
+    volumes:
+      - ./electron-update:/usr/share/nginx/html/electron-update
     environment:
       - NODE_ENV=production
     restart: unless-stopped