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/index.ts

@@ -30,7 +30,7 @@ import { txtToPdf } from './txt-to-pdf.js';
 import { invertColors } from './invert-colors.js';
 // import { viewMetadata } from './view-metadata.js';
 import { reversePages } from './reverse-pages.js';
-import { mdToPdf } from './md-to-pdf.js';
+// import { mdToPdf } from './md-to-pdf.js';
 import { svgToPdf } from './svg-to-pdf.js';
 import { bmpToPdf } from './bmp-to-pdf.js';
 import { heicToPdf } from './heic-to-pdf.js';
@@ -94,7 +94,7 @@ export const toolLogic = {
   'txt-to-pdf': txtToPdf,
   'invert-colors': invertColors,
   'reverse-pages': reversePages,
-  'md-to-pdf': mdToPdf,
+  // 'md-to-pdf': mdToPdf,
   'svg-to-pdf': svgToPdf,
   'bmp-to-pdf': bmpToPdf,
   'heic-to-pdf': heicToPdf,