Step 3: Invert state authority

### 📝 Description of the feature

Step 3 of the remote rendering work.
Move the state authority to the server. In a remote rendering configuration, the state needs to live on the server side, so we are moving it there for all configurations.

### Acceptance Criteria

Start VISOR locally. Change orientation, part visualization, color by variable, mesh visibility. Open the same session of VISOR in a different browser. The same visualization appears. The server-authorative state means all sessions pointing to the same web address are kept in sync.

### 💵 Business Value

_No response_

### 🔗 Useful links and references

_No response_

No files or tests are named in the issue. Start VISOR locally, exercise the listed visualization changes, and inspect the remote-rendering state flow before testing two browsers on the same web address. Done means all sessions show the same orientation, part visualization, variable coloring, and mesh visibility.

Rédigé par le modèle d'indexation à partir du texte de l'issue.