Feature: Add current and target network state to CRD

[xkonni]

Meta issue tracking the addition of network topology state to the ServerNetworkConfig CRD and related follow-up work.

Background

The ServerNetworkConfig CRD holds the expected network topology for a server (written by argora/NetBox via spec.interfaces) and the discovered state populated by metal-operator after each probe run (status.interfaces). The network check gates the Discovery → Available transition and is opt-in: an empty spec.interfaces means no constraint.

Open work

• Apply target network config on the host system
• Alert on topology changes
• Consolidate discovered interface data with the ServerMetadata proposal (Status loss during clusterctl move and its impact on Servers and ServerClaims #626)