Request: make the app port part of env config

[karanj]

Since the default port 3000 clashes with Grafana's default port, and I don't particularly want to mess with my existing Grafana setup, I had to change the config and code in a few places to allow me to start up the dev container without clashing with Grafana occupying port 3000.

Suggestion is to make the app port a config item in the .env file to enable easy changing of this attribute for those running with complex setups.