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.

索引モデルが issue の本文から書いたものです。