feat: add HOST env var

[makew0rld]

Description

In a similar vein as forbole/callisto#490, I am having a problem where there is no way to configure the Big Dipper UI server to only listen on loopback (127.0.0.1) instead of globally. This leaves my server with an open non-TLS port, when I'd rather have that port closed off to the world. In my setup I am using nginx to reverse-proxy big dipper, so I am running Big Dipper on port 3001, and ideally only ports 80 and 443 would be open on my server.

This PR fixes this issue by having a HOST env var that allows hosting on 127.0.0.1.

Checklist

• Ran Linting
• Targeted PR against correct branch.
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Wrote unit tests.
• Added an entry to the CHANGELOG.md file.
• Re-reviewed Files changed in the Github PR explorer.

[teamchong]

@huichiaotsou the code looks good to me
But moving forward, I am not sure if we should continue to use server/index.ts
as next start are provided by nextjs
and there are also Output File Tracing to generate minimal server.js

[huichiaotsou]

As discussed over slack, we should drop server/index.ts and use next.js built-in utils to build the app instead of express.js.

closed PR with issue created : #1037