feat: add contribution statistics dashboard

[islamhafez0]

Summary

Adds an interactive statistics dashboard that displays meaningful insights from GitHub contribution data, appearing below the generated chart.

Statistics Displayed

• Total Contributions - All-time contribution count across years
• Longest Streak - Maximum consecutive days with contributions
• Current Streak - Active streak counting from today
• Best Day - Day with highest contribution intensity
• Daily Average - Average contributions per day
• Busiest Day of Week - Which weekday you're most active
• Busiest Month - Which month you contribute most
• Year-over-Year - Growth percentage vs previous year (only shows if 2+ years of data)

Features

• Responsive grid layout (4 cols → 2 cols → 1 col)
• Supports light/dark mode using existing CSS variables
• Hover effects on stat cards
• Memoized calculations for performance
• Handles edge cases (empty data, single year, zero contributions)

[vercel]

@islamhafez0 is attempting to deploy a commit to the Github Contributions Chart Team on Vercel.

A member of the Team first needs to authorize it.