Enable basic type checking for cloud (#55337)

* Enable basic type checking for cloud

* Update mypy settings

* Address review comment

* Fix rebase mistakes

* Correct decorator order

homeassistant/components/cloud/utils.py

@@ -9,13 +9,17 @@ from aiohttp import payload, web
 def aiohttp_serialize_response(response: web.Response) -> dict[str, Any]:
     """Serialize an aiohttp response to a dictionary."""
     if (body := response.body) is None:
-        pass
+        body_decoded = None
     elif isinstance(body, payload.StringPayload):
         # pylint: disable=protected-access
-        body = body._value.decode(body.encoding)
+        body_decoded = body._value.decode(body.encoding)
     elif isinstance(body, bytes):
-        body = body.decode(response.charset or "utf-8")
+        body_decoded = body.decode(response.charset or "utf-8")
     else:
         raise ValueError("Unknown payload encoding")
 
-    return {"status": response.status, "body": body, "headers": dict(response.headers)}
+    return {
+        "status": response.status,
+        "body": body_decoded,
+        "headers": dict(response.headers),
+    }