Add zoom functionality to SenderPdfImageEditor

Introduced zoom controls to the `SenderPdfImageEditor` component, including zoom in/out, dynamic zoom levels, and a slider in the toolbar.

- Added zoom-related properties and methods to manage zoom levels.
- Updated the toolbar with zoom buttons and a slider for precise control.
- Enhanced JavaScript to handle zoom overrides and smooth scrolling.
- Modified UI elements to dynamically apply zoom styles.
- Improved accessibility and usability with appropriate attributes.
- Refactored code to integrate zoom functionality seamlessly.

These changes enhance the user experience by providing greater control over PDF viewing and editing.

EnvelopeGenerator.Server/EnvelopeGenerator.Server/wwwroot/js/envelope-editor.js

@@ -185,5 +185,45 @@ window.envelopeEditor = {
         const raw = bestPage.getAttribute('data-editor-page');
         const parsed = Number.parseInt(raw || '0', 10);
         return Number.isFinite(parsed) && parsed > 0 ? parsed : null;
+    },
+
+    scrollPdfViewerByDelta: function (viewerCssClass, deltaY) {
+        const viewer = document.querySelector('.' + viewerCssClass);
+        if (!viewer) {
+            return;
+        }
+
+        viewer.scrollTop += Number(deltaY) || 0;
+    },
+
+    ensureZoomOverride: function (viewerCssClass) {
+        const viewer = document.querySelector('.' + viewerCssClass);
+        if (!viewer) {
+            return;
+        }
+
+        if (viewer.dataset.zoomOverrideAttached === '1') {
+            return;
+        }
+
+        viewer.dataset.zoomOverrideAttached = '1';
+
+        viewer.addEventListener('wheel', function (event) {
+            event.preventDefault();
+        }, { passive: false });
+
+        viewer.addEventListener('keydown', function (event) {
+            if (!event.ctrlKey) {
+                return;
+            }
+
+            const key = event.key;
+            if (key === '+' || key === '=' || key === '-' || key === '0') {
+                event.preventDefault();
+            }
+        });
+
+        viewer.addEventListener('touchmove', function () {
+        }, { passive: true });
     }
 };