- Use jq for JSON payload construction (no more string interpolation)
- Add env_vars input — parsed into proper Portainer env array
- Add registry_url/user/pass inputs for private registry auth
- Fix pullImage: true on create path (was only on update)
- Add healthcheck polling loop with configurable retries/delay
- Fix stack_name default — resolve in script, not action default expression
- Rewrite README with full build+push+deploy example
