Multiple environment deployment strategy and infrastructure

Idea:
- a deploy to a staging environment (need to create this) should happen automatically when a push to `main` occurs
- a deploy to production environment should happen by intentional choice (usually after confirming things are all good in staging, but also perhaps after a hot-fix bug is remediated)

Pre-req: must build a new firebase/gcloud project environment.

@Justin-MacIntosh 's specific ideas based on his experience:
- local: working on a local branch
- dev: deployed from latest `main`, the environment QA testing happens on (similar to staging above)
- demo: deployed ad-hoc and untouched, used for showing people outside the team the product
- prod: deployed from latest GitHub release, the actual deployed product