Add pod/service/node proxy support

[cuppett]

Summary

Add support for the proxy subresource on Pods, Services, and Nodes, enabling arbitrary HTTP proxying through the Kubernetes API server.

Motivation

The proxy subresource allows making HTTP requests to a pod/service/node through the API server (e.g., GET /api/v1/namespaces/{ns}/pods/{name}/proxy/{path}). Used for accessing pod-hosted dashboards, health endpoints, and internal services without port-forwarding.

Implementation

• Add Proxyable contract with resourceProxyPath(string $path = ''): string
• Implement on K8sPod, K8sService, K8sNode
• Add proxy(string $method, string $path, ...) method that sends arbitrary HTTP requests through the proxy endpoint
• Must support all HTTP methods (GET, POST, PUT, DELETE, HEAD, OPTIONS, PATCH)

Effort: Large (complex HTTP proxying semantics)