feat: upgrade pdfjs-dist from 3.x to 5.x for improved PDF viewer

Update worker path from .js to .mjs to match the new ESM-only build
structure in pdfjs-dist v5. Core API (getDocument, getPage, render)
remains compatible.

package.json

@@ -63,7 +63,7 @@
     "marked": "^17.0.3",
     "marked-highlight": "^2.2.3",
     "pdf-lib": "^1.17.1",
-    "pdfjs-dist": "^3.11.174",
+    "pdfjs-dist": "^5.5.207",
     "pdfkit": "^0.14.0",
     "pizzip": "^3.2.0",
     "tslib": "^2.8.1",

src/renderer.js

@@ -4182,7 +4182,7 @@ let isPdfViewerActive = false; // Track if PDF viewer is currently shown
 
 // Initialize PDF.js
 const pdfjsLib = require('pdfjs-dist');
-pdfjsLib.GlobalWorkerOptions.workerSrc = require.resolve('pdfjs-dist/build/pdf.worker.js');
+pdfjsLib.GlobalWorkerOptions.workerSrc = require.resolve('pdfjs-dist/build/pdf.worker.mjs');
 
 // Open PDF file
 async function openPdfFile(filePath) {