React to CometChat activity in a Flutter app — SDK listeners (messages, calls, users, groups, connection) versus UI Kit events (CometChatMessageEvents, CometChatGroupEvents, CometChatUserEvents, CometChatConversationEvents), and the listener lifecycle that keeps them from leaking. Triggers: 'listen for new messages', 'react when a message is sent', 'cometchat listener flutter', 'unread badge count', 'onMessageReceived'.
