We’re talking about taking in React code and compiling it to iOS native UI plus the bridge between native APIs and JavaScript.
Obviously to get there you first need to get all the iOS UI kit into Pascal. Then also a compiler from Pascal to iOS binaries.
PS: don’t forget the dev tooling.
Are we talking about the site, or the web browser to view it with? I could probably do either in a month.
Using Lazarus/Free Pascal, about 1 week each.