feat: initial sunbeam CLI package

stdlib-only Python CLI replacing infrastructure/scripts/sunbeam.py.
Verbs: up, down, status, apply, seed, verify, logs, restart, get,
build, mirror, bootstrap. Service scoping via ns/name target syntax.
Auto-bundled kubectl/kustomize/helm (SHA256-verified, cached in
~/.local/share/sunbeam/bin). 63 unittest tests, all passing.

pyproject.toml

@@ -0,0 +1,12 @@
+[project]
+name = "sunbeam"
+version = "0.1.0"
+requires-python = ">=3.11"
+dependencies = ["setuptools"]
+
+[project.scripts]
+sunbeam = "sunbeam.__main__:main"
+
+[build-system]
+requires = ["setuptools>=68"]
+build-backend = "setuptools.build_meta"