- All logic in core layer (BackendServer runs independently)
- Packet protocol: {id, type, body} for all communications
- UI simplified: just input→backend→display
- Config, history, tools all handled by core
- BackendServer can run standalone without UI
- Add GET_CONFIG, SET_CONFIG, GET_HISTORY, SAVE_HISTORY to BackendServer
- Update BackendClient with get_config, get_message_history, save_message_history
- All API key and message history now stored in core layer