Add Streak System for Daily Practice and Performance Tracking

[devikrishna111]

📌 Description

This PR introduces a Streak System to the typing test application to encourage consistent practice and improve long-term engagement. Previously, the application only displayed performance metrics for a single session (such as WPM), making it feel session-based rather than growth-oriented.

The new streak system tracks user progress over time and adds a gamification element to motivate users to practice regularly.

🔗 Related Issue

Closes: #41

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🛠 Changes Made

• Implemented Daily Streak to track consecutive days the user completes at least one typing test.
• Added Improvement Streak to track sessions where WPM improves compared to the previous session.
• Implemented Personal Best Streak to track new highest WPM achievements.
• Added local data persistence using JSON (streak_data.json) to store streak information.
• Displayed streak statistics in the result summary/dashboard after each test.
• Implemented automatic daily streak reset when a day is missed.

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✅ Checklist

• [✅ ] I have tested my changes
• [ ✅] My code follows project guidelines
• [✅ ] I have linked the related issue