v1.1.0: Circular Chart with Threshold Support

🎉 New Features

SleepCircularChartView

• New circular chart component with percentage-based sleep duration visualization
• Configurable threshold system - set custom sleep duration targets (default: 9 hours)
• Optional sun/moon icons - toggle sleep start/end indicators on/off
• Percentage-based arc filling - starts at 12 o'clock and fills clockwise based on sleep duration vs threshold

🔧 API Changes

New Parameters

• thresholdHours: Double - Sleep duration threshold for percentage calculation (default: 9.0)
• showIcons: Bool - Display sun/moon icons at start/end of sleep arc (default: true)

Usage Examples

```swift
// Basic circular chart (9-hour threshold by default)
SleepCircularChartView(samples: sleepSamples)

// Custom threshold and styling
SleepCircularChartView(
samples: sleepSamples,
lineWidth: 20,
size: 200,
showIcons: false,
thresholdHours: 8.0
)
```

📚 Documentation

• Updated README with comprehensive circular chart documentation
• Added parameter descriptions and usage examples
• Updated architecture section with new components

🧪 Testing

• Added comprehensive test suite for circular chart functionality
• All existing tests continue to pass
• Verified Swift package compilation

💡 How it Works

If a user sleeps 7 hours with a 9-hour threshold, the circle fills 77.8% (7/9) of the way around, providing intuitive visual feedback on sleep goal progress.

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Full Changelog: v1.0.0...v1.1.0