Add multi-server node management support to S-UI

[Simon-xuan]

Description
Currently, S-UI only supports single-server configuration for node management, which can be limiting for multi-node deployments, load balancing, or managing servers across different regions. I propose adding multi-server node management support to S-UI, enabling users to:
1. Add, edit, and delete multiple server node entries from the panel.
2. Configure parameters for each node individually (such as address, port, protocol, certificates, etc.).
3. Quickly switch between and view the status/statistics of each node from the frontend interface.
4. Integrate with APIs for batch management and automated operations.

This feature would greatly enhance S-UI’s usability and flexibility in large-scale deployments and multi-region scenarios.

[Kagashini]

Approximate implementation: #954