feat(cli): Implement ability to set Production url

[leccles1]

Very basic implementation of including the ability to set a production url during celest build and celest start. As there doesn't appear to be a way to set this outside of running celest deploy. Would love to know if it is possible.

I haven't touched any tests, tbh the testing setup is very complex and I haven't quite been able to run the full suite yet. Any pointers on that I'd be happy to give it a shot.

Similarly the changes I have made appear to make the most sense to me whilst getting familiar with the repository, but alas, this is quite a large & complex codebase so any feedback, I'm happy to revisit the implementation.

• feat(cli): Implemented rudimentary production url setting which is applied during celest build or celest start