chore(ui): Global auth route protector

[andrewrisse]

Currently, every route has to have this code in its +page.server.ts file to ensure the user is redirected to / if their session has expired or doesn't exist.

We need a global route protector that can do this for all desired routes. Investigate if this can just be done with a parent +page.server.ts file and if so, why it's not working.

Test to ensure sessions that have expired are redirected to the login page (for example when a new message is sent in a thread rather than just failing with a 401 or 403.

 const session = await getSession();

  if (!session) {
    throw redirect(303, '/');
  }

Links to any relevant code

(optional) i.e. - https://github.com/defenseunicorns/uds-software-factory/blob/main/README.md?plain=1#L1

Additional context

Add any other context or screenshots about the technical debt here.