Fix mypy typing for admin message guard

apps/core/middleware.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import secrets
+from typing import Any, cast
 
 from django.contrib.messages import get_messages
 
@@ -54,7 +55,7 @@ class AdminMessageGuardMiddleware:
         # The public site has no legitimate use of Django's shared flash queue.
         # Drain any stale admin messages before frontend rendering can see them.
         if not request.path.startswith(self.ADMIN_PREFIXES):
-            storage = get_messages(request)
+            storage = cast(Any, get_messages(request))
             list(storage)
             storage._queued_messages = []
             storage._loaded_data = []