Implement Comment system

Allow users to create and view comments on code snippets. Create a form to submit new comments and display all comments for each snippet.

## Expectations

- Users can leave comments on code snippets.
- Comment form and all comments are displayed for each snippet when the comment button is clicked.
- Real-time updates are shown when new comments are added.

Start by locating the code-snippet view and its comment button in the React/TypeScript frontend, then trace the existing Redux state flow. Verify how comments should be created and loaded for each snippet. Done means users can submit comments, view all comments after opening the comment area, and see new comments update in real time.

Written by the indexing model from the issue text.