docs: add missing docs

ref: N25B-115

src/control_backend/api/v1/endpoints/sse.py

@@ -1,12 +0,0 @@
-from fastapi import APIRouter, Request
-
-router = APIRouter()
-
-
-# TODO: implement
-@router.get("/sse")
-async def sse(request: Request):
-    """
-    Placeholder for future Server-Sent Events endpoint.
-    """
-    pass