docs: add docs to CB

Pretty much every class and method should have documentation now.

ref: N25B-295

src/control_backend/schemas/llm_prompt_message.py

@@ -2,6 +2,17 @@ from pydantic import BaseModel
 
 
 class LLMPromptMessage(BaseModel):
+    """
+    Payload sent from the BDI agent to the LLM agent.
+
+    Contains the user's text input along with the dynamic context (norms and goals)
+    that the LLM should use to generate a response.
+
+    :ivar text: The user's input text.
+    :ivar norms: A list of active behavioral norms.
+    :ivar goals: A list of active goals to pursue.
+    """
+
     text: str
     norms: list[str]
     goals: list[str]