docs: add docs to CB

Pretty much every class and method should have documentation now.

ref: N25B-295

src/control_backend/main.py

@@ -1,3 +1,20 @@
+"""
+Control Backend Main Application.
+
+This module defines the FastAPI application that serves as the entry point for the
+Control Backend. It manages the lifecycle of the entire system, including:
+
+1.  **Socket Initialization**: Setting up the internal ZeroMQ PUB/SUB proxy for agent communication.
+2.  **Agent Management**: Instantiating and starting all agents.
+3.  **API Routing**: Exposing REST endpoints for external interaction.
+
+Lifecycle Manager
+-----------------
+The :func:`lifespan` context manager handles the startup and shutdown sequences:
+-   **Startup**: Configures logging, starts the ZMQ proxy, connects sockets, and launches agents.
+-   **Shutdown**: Handles graceful cleanup (though currently minimal).
+"""
+
 import contextlib
 import logging
 import threading
@@ -34,6 +51,12 @@ logger = logging.getLogger(__name__)
 
 
 def setup_sockets():
+    """
+    Initialize and run the internal ZeroMQ Proxy (XPUB/XSUB).
+
+    This proxy acts as the central message bus, forwarding messages published on the
+    internal PUB address to all subscribers on the internal SUB address.
+    """
     context = Context.instance()
 
     internal_pub_socket = context.socket(zmq.XPUB)