feat(ntfy): separate C&C topic from message ingestion

- 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

engine/config.py

@@ -105,6 +105,7 @@ class Config:
     firehose: bool = False
 
     ntfy_topic: str = "https://ntfy.sh/klubhaus_terminal_mainline/json"
+    ntfy_cc_topic: str = "https://ntfy.sh/klubhaus_terminal_mainline_cc/json"
     ntfy_reconnect_delay: int = 5
     message_display_secs: int = 30
 
@@ -148,6 +149,7 @@ class Config:
             mode="poetry" if "--poetry" in argv or "-p" in argv else "news",
             firehose="--firehose" in argv,
             ntfy_topic="https://ntfy.sh/klubhaus_terminal_mainline/json",
+            ntfy_cc_topic="https://ntfy.sh/klubhaus_terminal_mainline_cc/json",
             ntfy_reconnect_delay=5,
             message_display_secs=30,
             font_dir=font_dir,