feat(openviking-controlplane): enterprise tier, billing config, user management, stateless MCP 2026-07-28, and 0.2.0 release - #425

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-python@v5. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/