Improve error message for better understanding by users

[tiansiyuan]

The installation of docker on an Ubuntu 24.04.4 LTS requires root privilege to use it. Without root privilege, Strix outputs "DOCKER NOT AVAILABLE".

It is suggested to detect this situation and prompts accordingly.

[ttimasdf]

If you can't access docker socket, then docker is not available, literally.

[tiansiyuan]

If you can't access docker socket, then docker is not available, literally.

You are right.