Redirect wildcards

Hi,

We're changing our current web application to have a squarespace landing page, so that where we used to have "example.com", this will now be "app.example.com", and "example.com" will point to sqaurespace.

This is easy enough, however we need to allow for redirects for a lot of endpoints with wildcards.

What is the simplest way to have it redirect everything other than pages we have on square space? Failing that, what's the simplest way of having eg "example.com/page?123" and "example.com/page/321/something" to their "app.example.com" equivilient?

I've seen I can add header code into pages, but I believe this means I'd need to create every wildcard endpoint and add in a JS redirection for each of these?

Thanks!