feat: Add Analytics Dashboard page (analytics.html)

[Riya-Kharade]

📌 Description

This PR introduces a new Analytics Dashboard page to EcoPulse.

The dashboard provides a centralized pollution monitoring system that displays key environmental insights and analytics in one place.

closed #262

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✨ Changes Made

• Created new file: analytics.html
• Added summary cards:
  • Total Pollution Index
  • Highest Polluted City
  • Most Affected Pollution Type
  • Year Filter
• Implemented dynamic charts using Chart.js
• Added year-based filtering functionality
• Designed responsive dashboard layout using Tailwind CSS
• Applied EcoPulse theme styling
• Added navigation back to homepage

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🎯 Purpose

This feature:

• Enhances analytical depth
• Improves data visibility
• Makes EcoPulse look like a real monitoring platform
• Strengthens hackathon and portfolio presentation value
• Improves production readiness

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🧪 Testing

• Verified chart updates on year change
• Confirmed sorting logic for highest city and pollution type
• Tested responsiveness across devices
• Ensured UI consistency with existing theme

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Screenshot

No backend or additional dependencies were added.