Build Statistics Dashboard with Charts

**Title:** Create Personal Analytics Page with Comprehensive Performance Charts

## Problem Statement

Users lack detailed insights into their performance trends, learning patterns, and areas for improvement. A statistics dashboard would provide valuable analytics to help users track progress and optimize their learning.

## Proposed Solution

Create a comprehensive statistics/analytics page featuring:

* Performance over time graphs
* Category-wise accuracy charts
* Time management analytics
* Comparative performance metrics
* Heatmap of quiz activity
* Downloadable reports

## Acceptance Criteria

### ✅ Dashboard Layout

* Grid layout with multiple stat cards
* Responsive design (mobile/tablet/desktop)
* Collapsible sections for detailed views
* Date range selector (Last 7/30/90 days, All time)
* Export dashboard as PDF/PNG button
* Print-friendly version

### ✅ Performance Over Time Graph

* Line chart showing score trends
* X-axis: Date, Y-axis: Score percentage
* Multiple lines for different categories (optional)
* Interactive tooltips on hover
* Zoom and pan functionality
* Highlight personal best points
* Show trend line (moving average)

### ✅ Category Performance Chart

* Horizontal bar chart or radar chart
* Show accuracy percentage per category
* Color-coded bars (red/yellow/green)
* Sort options (Best to Worst, A-Z)
* Click bar to filter detailed questions
* Display question count per category

### ✅ Time Analytics

* Pie chart: Time distribution across categories
* Average time per question stat card
* Fastest quiz completion time
* Total time spent on quizzes
* Time of day heatmap (hour vs. day)
* Peak performance hours indicator

### ✅ Accuracy Analytics

* Overall accuracy percentage (large stat card)
* Accuracy by difficulty level (Easy/Medium/Hard)
* Most missed question types
* Improvement rate graph (week over week)
* Consecutive correct answers streak

### ✅ Activity Heatmap

* Calendar heatmap (GitHub-style)
* Color intensity based on quizzes completed
* Hover shows date and quiz count
* Current streak and longest streak display
* Perfect days (100% score) highlighted
* Gap identification for inactive periods

### ✅ Comparative Metrics

* Your rank vs. average user (simulated)
* Percentile ranking display
* Better/worse than average indicators
* Category-specific comparisons
* Speed vs. accuracy scatter plot

### ✅ Summary Cards

* Total quizzes completed
* Average score percentage
* Total time spent
* Current streak
* Highest score
* Total achievements earned
* Most improved category

### ✅ Detailed Tables

* Paginated table of all quiz attempts
* Columns: Date, Category, Score, Time, Questions
* Sort by any column
* Filter by date range, category, score range
* Export table as CSV
* Click row to view full quiz results

### ✅ Export Functionality

* Download dashboard as PDF
* Include all charts and summary stats
* Professional formatting
* Date range in filename
* Option to include or exclude graphs