[Feature Request] Restrict Admin Access and Control Initiation to Internal Network

Description:

I would like to request a security enhancement for RustDesk Server Pro to enforce strict network-based access controls. In enterprise environments, it is crucial to separate the permissions of the internal corporate network (where admins and support staff operate) from the public internet (where remote endpoints are located).

Specifically, we need the following two access restrictions:

1. Internal-Only Admin Access

There should be a configuration option (e.g., via IP whitelisting or interface binding) to restrict access to the Admin Panel. Logging into the RustDesk Server as an administrator should only be possible from specific internal subnets/IPs. Any login attempts from the public internet should be blocked.

2. Restrict Public Relay to "Target-Only" Mode (Block Control Initiation)

For the Relay server exposed to the public internet, we need a setting that allows external clients to register and receive connections (act as targets/hosts), but strictly blocks them from initiating remote control sessions against other users. The ability to control another machine (acting as a viewer/controller) should be strictly limited to users connecting from the internal network.

Use Case / Security Benefit:

This significantly reduces the attack surface. By implementing these restrictions, even if a bad actor compromises user credentials, they cannot access the admin console or use the public-facing relay to pivot and hijack other machines from outside the corporate network.

The issue names no files, tests, or entry points. Start by mapping the Admin Panel authentication path and public Relay connection roles, then identify existing configuration and network-boundary tests; done means internal-only admin login and target-only public relay behavior are configurable and covered by tests.