chore(license): add MIT LICENSE

[shtse8]

Adds an MIT LICENSE file to make the licensing of this repository explicit.

• This repository previously had no LICENSE file.
• Contents are original Sylphx-authored code (Dockerfiles, configs, scripts, and/or application/library source), not vendored upstream source, so MIT is the appropriate license.
• Copyright line: Copyright (c) 2026 Sylphx Limited.

Part of an org-wide docs-hygiene pass to ensure every original public repo carries an explicit license.