Dockerization works only on Ubuntu/Linux

[ATemova]

The Docker setup (docker compose) is supported only on Ubuntu/Linux.

Reasons:

• The Tkinter GUI needs the host X11 display (/tmp/.X11-unix), which is native on Linux but not on macOS/Windows (Docker Desktop runs in a VM, no direct display).
• The STM32 sensor uses USB/serial, which can be passed to a container with --device on Linux, but Docker Desktop on macOS/Windows does not support USB passthrough.

On macOS/Windows the API can still run in Docker, but the GUI and sensor must run natively. Documented as Linux-targeted in docker/README-docker-ubuntu.md.