Cut 16.1.1 and bump the package version in pyproject.toml, uv.lock,
and CITATION.cff.

Patch: Add the GitHub stars badge to README.md so repository support is
discoverable alongside the existing project badges (#125).

Changelog:
- Added the 16.1.1 section dated 2026-09-03 with the linked README
  badge entry for #125.

Docs: README.md already contains the GitHub stars badge from #125; no
other documentation changes are needed here.

Testing:
- uv run pytest -q -> 1112 passed, 15 skipped, 94% coverage
- uv run ruff check . && uv run ruff format --check . && uv run pyright
  -> clean, 0 errors, 0 warnings, 0 informations
- uv lock --check -> up to date
- uv run mkdocs build --strict -> clean; upstream advisory warning only