Add Unit Tests for Components

* **What:** Write unit tests for some of the React components to ensure they work as expected.

* **Why:** Tests are crucial for maintaining code quality and preventing regressions. They allow us to make changes to the codebase with more confidence.

* **How:**
1. The project uses `@testing-library/react` for testing. You can look at `App.test.js` for a basic example.
2. Pick a component, for example, `SideBar.js` or `ChatModal.js`.
3. Write a test file (e.g., `SideBar.test.js`) in the same directory as the component.
4. Write tests to check if the component renders correctly, if it responds to user interactions (like clicks), and if it displays the correct information based on its props.
5. You can run the tests using the `pnpm test` command.