Add WelcomeStats component and integrate session management in FlagQuiz

- Created a new WelcomeStats component to display user statistics and session results.
- Integrated session management in FlagQuiz, allowing users to track their performance across multiple sessions.
- Updated game state handling to include session completion and results display.
- Enhanced user experience with improved navigation and session reset functionality.

public/icons/medal-star.svg

@@ -1,4 +1,3 @@
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