Add document preview feature to wizard popup

Introduced a document preview feature in the `CreateEnvelopeWizardPopup` component. This includes:

- Injected `PdfRenderService` for rendering PDF pages.
- Replaced document metadata display with a preview card.
- Added `SenderPdfImageEditor` for interactive PDF previews.
- Implemented state management for preview pages and overlays.
- Added fallback logic to estimate PDF page count.
- Enhanced `ResetWizardState` to reset preview-related fields.
- Styled the preview card and wrap with new CSS classes.
- Added placeholder event handlers for editor interactions.

EnvelopeGenerator.Server/EnvelopeGenerator.Server/wwwroot/css/sender-page.css

@@ -1533,6 +1533,28 @@
     padding: 0.55rem 0.7rem;
 }
 
+.sender-create-wizard__document-preview-card {
+    display: flex;
+    flex-direction: column;
+    gap: 0.65rem;
+}
+
+.sender-create-wizard__document-preview-wrap {
+    border: 1px solid rgba(148, 163, 184, 0.38);
+    border-radius: 10px;
+    background: rgba(248, 250, 252, 0.96);
+    height: 320px;
+    overflow: hidden;
+}
+
+.sender-create-wizard__document-preview-wrap .sender-image-editor-shell {
+    height: 100%;
+}
+
+.sender-create-wizard__document-preview-wrap .sender-image-editor {
+    min-height: 0;
+}
+
 .sender-create-wizard__document-name {
     color: #064e3b;
     font-size: 0.85rem;