Add uv.lock for reproducible CI builds

The CI workflow uses `uv sync --frozen` which requires the lockfile
to be present. Remove uv.lock from .gitignore and commit it.

Author: tbhb

.gitignore

@@ -48,7 +48,6 @@ node_modules/
 # Python (for dev tools: codespell, vale, yamllint, prek)
 .venv/
 __pycache__/
-uv.lock
 
 # Local configuration
 mise.local.toml