⚡ perf: remove unnecessary SKShapeNode allocation

[jhurt]

💡 What: Replaced the explicit allocation of unusedCircleNode with mathematically derived dimensions (radius * 2.0) to calculate pageIndicatorWidth and pageIndicatorHeight in addIndicator().

🎯 Why: Creating a throwaway SKShapeNode simply to determine its resulting frame dimensions adds unnecessary overhead (CPU, memory allocation) during indicator setup.

📊 Measured Improvement: The swift and xcodebuild environments are unavailable to measure baseline and post-change performance. However, removing an unneeded object allocation inherently provides a net reduction in UI overhead by avoiding the initialization cost and garbage collection / reference counting overhead associated with SKShapeNode.

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PR created automatically by Jules for task 2944114691005413024 started by @jhurt

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