feat: add pollutant-specific map layers

[Suprita736]

Description

Implemented pollutant-specific map layers that allow users to view air quality data for individual pollutants such as PM2.5, NO₂, and Ozone instead of only the overall AQI.

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Related Issue

Closes #470

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Type of Change

• Bug Fix
• New Feature
• Documentation
• UI/UX Improvement
• Refactoring
• Performance Improvement
• Accessibility

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Changes Made

• Added pollutant-specific selection to the main Leaflet map.
• Added support for displaying pollutant concentration data on the map.
• Updated air quality service and TypeScript types to support pollutant-specific data.
• Added pollutant-specific color coding based on concentration/health breakpoints.
• Preserved the existing AQI map functionality.

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Testing

• Tested locally
• No console errors
• Existing functionality works as expected

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Screenshots

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Checklist

• My code follows the project guidelines.
• I have tested my changes.
• I have updated the documentation if required.
• My changes address the related issue.
• This PR focuses on a single issue.

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Additional Notes

The implementation focuses specifically on Issue #470 and does not intentionally modify unrelated functionality.

[vercel]

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[github-actions]

Thank You for Your Contribution! 🎉

Hi @Suprita736,

Thank you for opening this Pull Request and contributing to our project. We truly appreciate your efforts.

Please make sure that:

• Your code follows the project's guidelines.
• You have linked the appropriate issue (if applicable).
• Screenshots are added for UI/UX changes.
• Your PR is ready for review.

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