Refactor redirect for plans page to not require a react-router version upgrade

[RuthShryock]

Checklist

1. If you've added code that should be tested, add tests
2. If you've changed APIs, update (or create!) the documentation
3. Ensure the tests pass
4. Make sure that your code lints and that you've followed our coding style
5. Write a title and, if necessary, a description of your work suitable for publishing in our release notes
6. Mention any related issues in this repository (as #ISSUE) and in other repositories (as kobotoolbox/other#ISSUE)
7. Open an issue in the docs if there are UI/UX changes

Description

Original redirect pr required a react-router version upgrade which was throwing an AwaitRenderStatus reference error, see internal discussion: https://chat.kobotoolbox.org/#narrow/stream/4-Kobo-Dev/topic/2.2E023.2E52.20release/near/318048

Notes

Reverting react-router version back to 6.14.2 and commenting out the authLoader function which was dependent on the upgrade. Moved PROJECTS_ROUTES to jsapp/js/projects/routes.tsx to prevent circular dependency errors and updated the requireAuth component to redirect appropriately based on the user's login status.