refactor(qpdf): move initialization logic to helpers module

Consolidate qpdf initialization code into helpers.ts to avoid duplication
Improve error message for password protected PDFs
Fortify encryption logic by auto-filling owner password when empty

src/js/logic/decrypt.ts

@@ -1,31 +1,6 @@
 import { showLoader, hideLoader, showAlert } from '../ui.js';
-import { downloadFile, readFileAsArrayBuffer } from '../utils/helpers.js';
+import { downloadFile, initializeQpdf, readFileAsArrayBuffer } from '../utils/helpers.js';
 import { state } from '../state.js';
-import createModule from '@neslinesli93/qpdf-wasm';
-
-let qpdfInstance: any = null;
-
-async function initializeQpdf() {
-  if (qpdfInstance) {
-    return qpdfInstance;
-  }
-  showLoader('Initializing decryption engine...');
-  try {
-    qpdfInstance = await createModule({
-      locateFile: () => '/qpdf.wasm',
-    });
-  } catch (error) {
-    console.error('Failed to initialize qpdf-wasm:', error);
-    showAlert(
-      'Initialization Error',
-      'Could not load the decryption engine. Please refresh the page and try again.'
-    );
-    throw error;
-  } finally {
-    hideLoader();
-  }
-  return qpdfInstance;
-}
 
 export async function decrypt() {
   const file = state.files[0];