Add ability to change front end port tcp:3000 to something else

I haven't customized a windows machine much but run into an error when trying to start up the assistant locally. Meaning, Open-Assistant is trying to use a port is in use by a system process.

OS Name	Microsoft Windows 11 Pro
Version	10.0.22621 Build 22621

PS C:\Users\kylem\Development\Open-Assistant> docker compose --profile ci up --build --attach-dependencies
...
Attaching to open-assistant-backend-1, open-assistant-backend-worker-1, open-assistant-backend-worker-beat-1, open-assistant-db-1, open-assistant-maildev-1, open-assistant-redis-1, open-assistant-web-1, open-assistant-webdb-1
Error response from daemon: driver failed programming external connectivity on endpoint open-assistant-web-1 (ccce9108f9ee2bfe52bc2f6a77028b76e2a08935906fbd345164d1f727215a17): listen tcp4 0.0.0.0:3000: bind: address already in use

> netstat -ano
TCP    0.0.0.0:3000           0.0.0.0:0              LISTENING       4788

the 4788 process listening on port 3000 is https://en.wikipedia.org/wiki/Svchost.exe.

My quick work around

I searched the repository and changed any instance of 3000 (that was specific to networks) to 3239. The 3239 number was chosen by random human fingers.

open-assistant-web-1                  | Listening on port 3239 url: http://localhost:3239

It works 👍 . I'm not suggesting this as the solution, but this repository could use an environment variable or some other mechanism to change the number when there is a conflict.

No file or test is named. Start with the docker-compose frontend service and search the repository for the port 3000 references; confirm how the frontend port and local URL are configured. Done means a user can select another port and start the assistant successfully on Windows without a port conflict.