refactor: ZMQ context and proxy

Use ZMQ's global context instance and setup an XPUB/XSUB proxy intermediary to allow for easier multi-pubs.

close: N25B-217

src/control_backend/core/config.py

@@ -3,7 +3,8 @@ from pydantic_settings import BaseSettings, SettingsConfigDict
 
 
 class ZMQSettings(BaseModel):
-    internal_comm_address: str = "tcp://localhost:5560"
+    internal_pub_address: str = "tcp://localhost:5560"
+    internal_sub_address: str = "tcp://localhost:5561"
 
 
 class AgentSettings(BaseModel):
@@ -24,6 +25,7 @@ class LLMSettings(BaseModel):
     local_llm_url: str = "http://localhost:1234/v1/chat/completions"
     local_llm_model: str = "openai/gpt-oss-20b"
 
+
 class Settings(BaseSettings):
     app_title: str = "PepperPlus"
 
@@ -37,4 +39,5 @@ class Settings(BaseSettings):
 
     model_config = SettingsConfigDict(env_file=".env")
 
+
 settings = Settings()

src/control_backend/core/zmq_context.py

@@ -1,3 +0,0 @@
-from zmq.asyncio import Context
-
-context = Context()