Add real-time collaboration

Problem/Motivation

Because we are already storing the data state in server side only (browser side is stateless) and our State Maanger ahs already proved its robustness when we edit same data from multiple users, we will be able to activate real-time collaboration once those 2 issues are done:

• 📌 [1.0.0-alpha2] Better logs Active : user ID will be stored in logs
• bigskysoftware/htmx: Combining sse and oob

Proposed resolution

Everytime an user is updating the data state, a SSE event is sent to other users editing the same display.

It would be nice to show in the toolbar the ID of other connected users.

Out of scope

We don't show the cursor of the other users on the screen like Figma is doing. Let's keep it simple and light, leveraging what HTML is providing and not much more.