Make zoom step percentage configurable

Added a `ZoomStepPercentage` property to `PdfViewerOptions` to allow configurable zoom step increments (1-50, default 5%). Updated `EnvelopeViewer.razor` to use this property for the zoom slider step. Modified `pdf-viewer.js` to apply the zoom step percentage for mouse wheel zoom, `zoomIn`, and `zoomOut` methods.

Included `ZoomStepPercentage` in `appsettings.json` and `setQualityOptions` for dynamic updates. Reduced `ZoomTransitionDuration` in `appsettings.json` from 900ms to 150ms for faster zoom transitions. These changes ensure consistent and customizable zoom behavior across the application.

EnvelopeGenerator.ReceiverUI/Options/PdfViewerOptions.cs

@@ -61,4 +61,11 @@ public class PdfViewerOptions
     /// Default: 50
     /// </summary>
     public int ThumbnailRenderDelay { get; set; } = 50;
+
+    /// <summary>
+    /// Zoom step percentage (1 - 50)
+    /// Controls how much zoom changes per click or scroll
+    /// Default: 5 (5% per step)
+    /// </summary>
+    public int ZoomStepPercentage { get; set; } = 5;
 }