refactor: misc code quality improvements (#6)

* refactor: misc code quality improvements

- pep518.go: replace deprecated ioutil.ReadFile with os.ReadFile
- pep518.go: replace panic with log.Error + early return on read failure
- poetry.go: fix CWD-relative fileExists bug (filepath.Join path+poetry.toml)
- run.go: ExecutePython delegates to GetPythonRunCommand; drop redundant else
- uv/pipenv/pip/poetry.go: simplify log.Error(fmt.Sprintf("%s", err.Error())) to log.Error(err.Error())
- go mod tidy

* refactor: restore inline comments removed during cleanup

Update logrus

Add GetPythonRunCommand public method to return a cmd instance

Update README and add MIT license

Make ExecutePython usable from package