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.

.gitignore

@@ -0,0 +1,6 @@
+__pycache__/
+*.py[cod]
+*.egg-info/
+dist/
+build/
+.eggs/