Dev: Use multi-stage build for front-end

We should use a multistage build for the front-end to prevent embedding our artifactory npm token in the final image.

Start by locating the front-end container build and the configuration that installs npm dependencies. Check how the artifactory token enters the build, then verify that the final image can run without retaining that token. Done means the front end still builds successfully and the token is absent from the final image.

Written by the indexing model from the issue text.