Make aks-mcp stdio-only and remove remote deployment support

## Breaking change

The next major release will support only the MCP stdio transport. SSE and streamable HTTP transports, container-image distribution, and Kubernetes/Helm deployment artifacts will be removed.

## Rationale

This project is a local MCP server. It executes local command-line tools using the identity of the MCP process, and it is not intended to expose those tools as a remote service.

## Scope

- Remove SSE and streamable HTTP runtime support.
- Remove HTTP-only authentication, token forwarding, and network configuration.
- Remove token-only authentication and AKS RunCommand execution support.
- Remove Helm/Kubernetes deployment artifacts and documentation.
- Stop building, publishing, signing, and attesting container images and Helm charts.
- Retain local stdio execution and binary releases.

## Migration

Install the released binary locally and configure your MCP client to start it as a stdio subprocess. Remote deployments must not be upgraded in place; move the client configuration to a local stdio installation instead.

## Out of scope

This change does not remove the optional Helm MCP tool. That capability will be evaluated separately.

Inventory the runtime, authentication, network, Kubernetes/Helm, container, and release configuration referenced by the issue, then trace how stdio execution is wired. Remove the listed remote and deployment paths while retaining local stdio execution and binary releases; verify that container and Helm artifacts are no longer built or published.

Written by the indexing model from the issue text.