Add Monthly Category-wise Pie Chart Visualization with Dynamic Updates

[devikrishna111]

📌 Description

This PR enhances the Expense Tracker by adding a category-wise analytical visualization feature.

Users can now filter expenses by month and view a dynamic Pie Chart that displays category-wise totals and percentage distribution for the selected month.

The chart updates automatically whenever expenses are added, edited, or deleted.

🔗 Related Issue

Closes #28

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🛠 Changes Made

• Added month-based filtering for expense analysis
• Grouped expenses by category within selected month
• Integrated Chart.js to display category-wise Pie Chart
• Implemented percentage calculation for each category
• Enabled dynamic chart updates on add/edit/delete actions
• Improved UI by resizing chart to medium responsive layout

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✅ Checklist

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