feat: add ENABLE_ADMIN_CHAT_ACCESS to control admin access to user chats

backend/config.py

@@ -824,6 +824,10 @@ WEBHOOK_URL = PersistentConfig(
 
 ENABLE_ADMIN_EXPORT = os.environ.get("ENABLE_ADMIN_EXPORT", "True").lower() == "true"
 
+ENABLE_ADMIN_CHAT_ACCESS = (
+    os.environ.get("ENABLE_ADMIN_CHAT_ACCESS", "True").lower() == "true"
+)
+
 ENABLE_COMMUNITY_SHARING = PersistentConfig(
     "ENABLE_COMMUNITY_SHARING",
     "ui.enable_community_sharing",