refactor: fix type errors and improve type safety in PDF logic

- Add proper type assertions for DOM element properties
- Remove unused md-to-pdf feature
- Fix type errors in various PDF manipulation functions
- Improve type safety for HTML element interactions

src/js/logic/decrypt.ts

@@ -16,8 +16,7 @@ export async function decrypt() {
 
   try {
     showLoader('Preparing to process...');
-    const pdfData = await readFileAsArrayBuffer(file);
-    // @ts-expect-error TS(2304) FIXME: Cannot find name 'pdfjsLib'.
+    const pdfData = (await readFileAsArrayBuffer(file)) as ArrayBuffer;
     const pdf = await pdfjsLib.getDocument({
       data: pdfData,
       password: password,