Add unit tests for api/validators language code validation - #99

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: tj-actions/changed-files@v45. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

No file matched to [/home/runner/work/Scribe-Server/Scribe-Server/**/*requirements*.txt,/home/runner/work/Scribe-Server/Scribe-Server/**/*requirements*.in,/home/runner/work/Scribe-Server/Scribe-Server/**/*constraints*.txt,/home/runner/work/Scribe-Server/Scribe-Server/**/*constraints*.in,/home/runner/work/Scribe-Server/Scribe-Server/**/pyproject.toml,/home/runner/work/Scribe-Server/Scribe-Server/**/uv.lock,/home/runner/work/Scribe-Server/Scribe-Server/**/*.py.lock]. The cache will never get invalidated. Make sure you have checked out the target repository and configured the cache-dependency-glob input correctly.