[FEATURE] Add time usage breakdown visualization by category

[Hasini2706]

📌 Description

Implemented a responsive time usage analytics dashboard with category-wise visualization using Recharts.

🔗 Related Issue

Closes #414

🛠 Changes Made

• Added category-wise time analytics
• Implemented donut chart visualization using Recharts
• Added task duration support
• Added total planned hours calculation
• Added most used category insights
• Integrated analytics into dashboard
• Added empty state handling
• Improved backend validation for duration fields
• Fixed dashboard routine loading integration

📸 Screenshots (if applicable)

Added analytics dashboard screenshots.

✅ Checklist

• Code runs locally
• Followed project structure
• No console errors
• Properly tested changes
• Linked the issue

🚀 Notes for Reviewers

Tested task creation, duration aggregation, category analytics, responsive UI, and production build successfully.

[Hasini2706]

Hi maintainers 👋

This PR implements the time usage breakdown analytics feature with category-wise visualization, responsive charts, and backend integration.

The feature has been tested locally and production build works correctly. GitHub Actions appear to be awaiting maintainer approval for workflow execution.

Would appreciate a review whenever available. Thanks!