test: add first unit test for VAD agent

Mocking audio input probabilities, checking whether it publishes audio data on the output socket.

ref: N25B-213

src/control_backend/core/config.py

@@ -6,9 +6,6 @@ from pydantic_settings import BaseSettings, SettingsConfigDict
 class ZMQSettings(BaseModel):
     internal_comm_address: str = "tcp://localhost:5560"
 
-    audio_fragment_port: int = 5561
-    audio_fragment_address: str = f"tcp://localhost:{audio_fragment_port}"
-
 
 class AgentSettings(BaseModel):
     host: str = "localhost"