QScatterSeries provides setSelectedColor() for fill color of selected points, but there's no corresponding setSelectedBorderColor() API for border styling of selected points specifically.

Feature request: 

Introduce a new API to set the border color for selected points, e.g.:
QScatterSeries::setSelectedBorderColor(const QColor &color);
This addition would complement the existing setSelectedColor() method and allow developers to fully customize the appearance of selected scatter points.

Current APIs:

• ✅ setSelectedColor() - Works for fill color
• ❌ setSelectedBorderColor() - Missing

Impact:

• Cannot achieve "selected points with different border color" without workarounds
• Forces use of separate QScatterSeries for selected points (performance overhead)
• Inconsistent API design (has selected fill color but not selected border color)

Current Workaround

// Must use separate series for selected points
QScatterSeries* selectedSeries = new QScatterSeries();
selectedSeries->setColor(QColor(255, 46, 255)); // Magenta
selectedSeries->setBorderColor(QColor(0, 204, 0)); // Green border
// Manually sync selected points between series

Expected Behavior{}{}

// Desired API that should exist:
scatterSeries->setSelectedColor(QColor(255, 46, 255)); // Magenta fill
scatterSeries->setSelectedBorderColor(QColor(0, 204, 0)); // Green border