I'm Andres Clari from SteelCode Consulting, and I have ample experience building sites using jQuery, Bootstrap, and recently I built a whole site which Rails only provided the backend and all the frontend was done in EmberJS, so I can handle dynamic the frontends perfectly.
So I feel I can help you with anything you might need for this project.
From your spec, I assume you'd be hooking the "login" function when the login button is clicked yourself? I shall only provide the hook for it?
Depending on what you need there I can call any function you need, or provide an Ajax post function to send the form to the server.
Let me know if you want to work together on this.
Regards, Andres.