feat(cli): add bundled health app scaffold and init command

- ship OpenAPI-first health check template as package data
- add CLI to copy scaffold into new project directories
- include OpenAPI spec, routes, and bootstrap example
- enable fast startup for OpenAPI-first services

openapi_first/templates/health_app/routes.py

@@ -0,0 +1,2 @@
+def get_health():
+    return {"status": "ok"}