Add packaging metadata so python -m build works

#110 recorded pyproject.toml + __init__.py as verified on a real toolchain
but they were never committed; origin has nothing past d5203ce.

pyproject.toml is deliberately plain: the sidecar's pypi.ReadProjectMetadata
is a line scanner, not a TOML parser, and reads name and version as literal
single-line assignments under [project]. A dynamic version would break both
the publish check and the startup reconcile.

__init__.py re-exports the public API so src/i7lib is an importable package.
.gitignore keeps dist/ out of the tree — a committed wheel would travel in
gitea's source archive and trip the builder's one-wheel-in-dist check.

.gitignore

@@ -0,0 +1,5 @@
+dist/
+build/
+*.egg-info/
+__pycache__/
+*.pyc