Windows build for Faktura POS

1. Install JDK 21+ on Windows (includes jpackage).
2. Open Command Prompt in the POS folder.
3. Run: windows\build-installer.bat
4. The installer .exe will be created in installer-output\

The installer bundles the POS application and a Java runtime, so the target machine does not need Java installed separately.
The POS app runs on http://localhost:8085
