Merge pull request #7 from CSOgroup/dev

Reorganize repo structure and update installation docs

- Move CONTRIBUTING.md, CODE_OF_CONDUCT.md to .github/
- Move environment.yml, cran-comments.md to dev/
- Rewrite INSTALLATION.md with clearer structure and troubleshooting
- Switch install examples to pak::pak() (devtools::install_github deprecated)
- Add *.tar.gz, src/*.so, src/*.o to .gitignore; untrack compiled binary
- Regenerate man/ Rd files; trim .Rbuildignore

Merge pull request #2 from CSOgroup/v1.5

v1.5

updated website and minor changes