This PR implements a new screen that allows users to view all available questions with a clear visual indication of which ones they've already read. The implementation:

1. Creates a dedicated /questions page that displays all questions with read status indicators
2. Adds a client-side component (ReadStatusItem) that shows different visual indicators for read vs unread questions
3. Modifies the existing ListOfQuestions component to conditionally show read status
4. Updates the Header to link to the questions page from the existing read counter

Visual indicators

Questions are marked with:

• Green dot: Questions that have been read
• Gray dot: Questions that haven't been read yet

The questions page includes a legend explaining these indicators, making it easy for users to understand which questions they still need to review.

Technical implementation

The implementation leverages the existing localStorage mechanism for tracking read questions (used by ButtonRead). The new component listens for storage events to ensure the UI updates if questions are marked as read/unread in another tab.

This feature provides users with a guide to track their progress through the content, making it easier to plan which material to consume next.

Fixes #47.

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