[Feature]: use an hardened Docker image

[eze-kiel]

Describe the solution you'd like

Statically compile cfcr and use a scratch base image in the last build stage. This will reduce the attack surface and attacker's capabilities in case of compromise.

Additional context

Having FROM scratch images may make the debugging process more complex (no shell nor privileges...).

Let's discuss about it if you're interested in the the idea @xakraz :0)