Retrieve Node Data from kubectl Instead of NeuVector

Description

Refactor the node data retrieval logic in the backend to pull directly from the Kubernetes API using kubectl or a Kubernetes client (e.g., client-go), rather than relying on NeuVector output. This ensures more accurate and real-time infrastructure visibility.

Acceptance Criteria:

• Replace NeuVector node data with data fetched from kubectl get nodes -o json or equivalent API call

• Parse and normalize relevant metadata (name, status, labels, roles, etc.)

• Update the dashboard to reflect the new source

• Update tests and mocks to cover the new implementation