Replace `rxjs` and `@ngneat` with idiomatic React

[tyler-dane]

RXJS is a fine library, but it's overkill for the web app, making it unnecessarily difficult to read and update. The same features we use RxJs for can be implemented using standard React

• Replace RxJs with React
• Remove rxjs dependency from web project
• Do the same for ngneat, replacing with either React or Redux

Context

https://www.reddit.com/r/reactjs/comments/11oge4h/is_rxjs_commonly_used_in_reactjs_for_reactive/