Fix zoom behavior for high-resolution touchpads

[retsubhtym]

• Use qRound() for precise event positions.
• Handle pixelDelta() when angleDelta() is zero to support smooth scrolling on high-resolution touchpads. angleDelta() is unreliable for modern touchpads, as some devices report finer scroll steps via pixelDelta().
• Adjust zoom scaling with qPow() for better granularity