Add notification alert on receiving message from anyone.

Hello contributors, this project already uses `react-hot-toast`, someone just have to trigger it on receiving any message, If you have any doubt you can ask me.

Start by locating the existing react-hot-toast setup and the client-side handler for receiving messages through the real-time chat flow. Trigger a toast whenever any incoming message is received, then verify that the alert appears for messages from any sender without disrupting normal message display.

Written by the indexing model from the issue text.