Add "user is online" indicator in users table

### Description

Add a green dot next to the user icon if a user has an active VPN session.

<img width="448" height="600" alt="Image" src="https://github.com/user-attachments/assets/b5b4be80-6b95-4379-8565-587caa0a34d1" />

https://www.figma.com/design/dZgIk8Ph3EXT0pGfH51MAW/Core?node-id=2622-63284&m=dev