Bump MCP Gateway (mcpg) to v0.4.1

[lpcox]

Summary

Bump the MCP Gateway from v0.3.33 to v0.4.1.

Note: This is a minor version bump (0.3 → 0.4) — check release notes for breaking changes.

Changes needed

Update pkg/constants/version_constants.go:

const DefaultMCPGatewayVersion Version = "v0.4.1"

Checklist

• Update DefaultMCPGatewayVersion in pkg/constants/version_constants.go
• Run make recompile to update lock files referencing the gateway image
• Verify smoke tests pass with new version
• Check release notes for breaking changes requiring codemod or config updates

Release notes

https://github.com/github/gh-aw-mcpg/releases/tag/v0.4.1