New web UI

Byline's web version could probably benefit from a page-based interface. Instead of showing and hiding alert boxes and disabling/enabling form elements, it would switch between pages depending on the current login/server status.

<img width="1920" height="1080" alt="Image" src="https://github.com/user-attachments/assets/5a0509c3-dce4-4947-b422-1aca2cfde336" />