Fix produce-box select cancelling config entry setup

async_added_to_hass listed the switchable boxes inline, one fetch per box
popup, so on a slower connection the platform setup ran past
SLOW_SETUP_MAX_WAIT and the whole config entry was cancelled into
setup_error — every entity unavailable despite valid credentials. Move the
listing to a background task so setup never blocks on it; the options fill in
once it returns.

Also bound every portal request to a 30s timeout so one hung request can no
longer drag a refresh, or a first setup, past Home Assistant's own limits and
fail it outright.

Regression covered in tests/test_setup_hygiene.py.

tests/test_parser.py

@@ -26,6 +26,7 @@ def _load_api():
         stub = types.ModuleType("aiohttp")
         stub.ClientSession = object
         stub.ClientError = Exception
+        stub.ClientTimeout = lambda *args, **kwargs: None
         sys.modules["aiohttp"] = stub
     if "yarl" not in sys.modules:
         try: