Add packaging/ with entry scripts and build_exes.py: the CLI is frozen with
PyInstaller (one-file console) and the GUI with `flet pack` (PyInstaller plus
the bundled Flet desktop runtime). Both bundle settings.yaml as data so the
frozen binaries load their defaults via importlib.resources, and the script
zips the results into release/ for upload.
Bump version to 2.0.0a0, gitignore build artifacts (*.exe, *.zip, *.spec,
dist/build/release), add a `build` extra, and document pre-built binaries and
the build process in the README.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
