- Add ntfy_cc_topic config for command and control
- Add separate NtfyPoller for C&C in StreamController
- Implement serial-port-like interface: commands are executed and responses are sent back to the same topic
- Update cmdline.py to use C&C topic
- Refactor controller to not require importing engine.layers (which imports PIL)
- Add set_effect_chain_ref for external chain registration
- Fix cmdline to use new ref mechanism