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/wwwroot/appsettings.json

@@ -4,14 +4,16 @@
     "ForceToUseFakeDocument": false
   },
   "PdfViewer": {
+    "_comment": "PDF Viewer Quality Settings - Changes are applied automatically via IOptionsMonitor",
     "ThumbnailBaseScale": 0.75,
     "ThumbnailEnableHiDPI": true,
     "ThumbnailMaxDPR": 2.0,
     "MainCanvasEnableHiDPI": true,
     "MainCanvasMaxDPR": 2.0,
     "EnableSmoothZoom": true,
-    "ZoomTransitionDuration": 900,
+    "ZoomTransitionDuration": 150,
     "RenderingOpacity": 0.85,
-    "ThumbnailRenderDelay": 50
+    "ThumbnailRenderDelay": 50,
+    "ZoomStepPercentage": 5
   }
 }