chore(heatmap): evaluate and integrate react-calendar-heatmap to replace custom PointsHeatmap

Description:

This MR evaluates replacing the existing custom heatmap implementation (PointsHeatmap.tsx) built using Recharts with the dedicated library react-calendar-heatmap.

A spike was performed to map the current data structure to the library’s required format. The library successfully supports core features such as date-based activity visualization, color scaling, and tooltips. Based on the evaluation, the custom component has been replaced/reviewed (adjust depending on your final work).

This change reduces maintenance overhead and improves UI consistency while leveraging a purpose-built solution. Type of Change:

• Bug Fix
• Feature Development
• Documentation

Testing:

• Tested on desktop
• Tested on mobile
• Tested in different browsers

Screenshots (if applicable):

Add screenshots for UI changes.

Video Demo

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If you have used AI create this PR, please also record video of yourself explaining the changes.

Link to code walkthrough

Checklist:

• Code follows project style guidelines
• Self-review completed
• No console errors
• TypeScript types are correct