When running with a custom `PORT` env variable, NGINX server will be
listening on this port. In the backend's startup script, `run-java.sh`,
we're checking for RTS being up or not, at `localhost`. So when the port
is not 80, then this will never succeed, because it'll be looking for
NGINX at the wrong port.
Instead, the fix here will make the backend startup script hit RTS
_directly_ on RTS server's own port, instead of going via NGINX. This
means it's independent of both the `PORT` env variable and the NGINX
server, and only dependent on RTS being up, which is really what we want
here.
Move the files that are copied into the Docker image, into an `fs`
folder, that reflects the folder structure of that in the image. This
means two things right away:
1. A single `COPY` instruction in `Dockerfile` is enough to copy all the
files to their places.
2. The structure of files in the repo reflects that in the Docker image.
This makes working with the files/folders and troubleshooting with them
much easier.
❗ Note: **There's actually only 3 files changed, rest are just moved.**
