refactor: update renderer.js to use ModalManager for all dialogs

- Import ModalManager and create instances for all 10 dialogs
- Replace classList.add/remove('hidden') with modal.open()/close()
- Remove duplicate backdrop click and escape key handlers (now handled by ModalManager)
- Update print-preview.js to use ModalManager when available
- Add CommonJS export to ModalManager for renderer compatibility

Dialogs updated:
- find-dialog (findModal)
- export-dialog (exportModal)
- print-preview-overlay (printPreviewModal)
- table-generator-dialog (tableModal)
- ascii-art-dialog (asciiModal)
- universal-converter-dialog (converterModal)
- batch-dialog (batchModal)
- pdf-editor-dialog (pdfEditorModal)
- header-footer-dialog (headerFooterModal)
- field-picker-dialog (fieldPickerModal)

Amit Haridas

src/print-preview.js

@@ -1,19 +1,28 @@
 class PrintPreview {
     constructor() {
         this.overlay = document.getElementById('print-preview-overlay');
+        this.modal = window.modals?.printPreviewModal;
         this._lastContent = '';
         this.setupEventListeners();
     }
 
     open(htmlContent) {
         this._lastContent = htmlContent;
-        this.overlay.classList.remove('hidden');
+        if (this.modal) {
+            this.modal.open();
+        } else {
+            this.overlay.classList.remove('hidden');
+        }
         this.updatePreview(htmlContent);
         this.updateScaleLabel();
     }
 
     close() {
-        this.overlay.classList.add('hidden');
+        if (this.modal) {
+            this.modal.close();
+        } else {
+            this.overlay.classList.add('hidden');
+        }
     }
 
     setupEventListeners() {
@@ -38,17 +47,7 @@ class PrintPreview {
             }
         });
 
-        // Close on overlay click
-        this.overlay?.addEventListener('click', (e) => {
-            if (e.target === this.overlay) this.close();
-        });
-
-        // Close on Escape
-        document.addEventListener('keydown', (e) => {
-            if (e.key === 'Escape' && !this.overlay.classList.contains('hidden')) {
-                this.close();
-            }
-        });
+        // Note: Backdrop click and Escape key are now handled by ModalManager
     }
 
     updateScaleLabel() {