[Remote rendering 5.2] Replace local render window with pvserver connection

### 📝 Description of the feature

Implement ParaView's pvserver client connection so RemoteRenderer renders against pvserver instead of the local render-window stand-in used by the initial spike, then remove that stand-in.

Re-verify the Phase 4 behaviour (streaming, per-part state, camera interaction, coalescing, connect/reconnect, live refresh) against the real ParaView server backend.

### Acceptance Criteria

Remote rendering behaviour holds with pvserver as the backend.

### 💵 Business Value

_No response_

### 🔗 Useful links and references

_No response_

首先定位初始 spike 中的 RemoteRenderer 和本機 render-window 替代實作。檢查目前如何驗證 Phase 4 的行為，然後將渲染連接到 pvserver 並移除替代實作。當 streaming、按部件狀態、相機互動、合併、連線/重新連線以及即時重新整理都能透過真正的 ParaView 伺服器後端正常運作時，即表示完成。

由索引模型根據 Issue 內容生成。