feat: parameterize RI host

Was "localhost" in RI Communication Agent, now uses configurable setting. Secretly also removing "localhost" from VAD agent, as its socket should be something that's "inproc".

ref: N25B-352

src/control_backend/core/config.py

@@ -125,6 +125,7 @@ class Settings(BaseSettings):
 
     :ivar app_title: Title of the application.
     :ivar ui_url: URL of the frontend UI.
+    :ivar ui_url: The hostname of the Robot Interface.
     :ivar zmq_settings: ZMQ configuration.
     :ivar agent_settings: Agent name configuration.
     :ivar behaviour_settings: Behavior configuration.
@@ -137,6 +138,8 @@ class Settings(BaseSettings):
 
     ui_url: str = "http://localhost:5173"
 
+    ri_host: str = "localhost"
+
     zmq_settings: ZMQSettings = ZMQSettings()
 
     agent_settings: AgentSettings = AgentSettings()