fix(pdf): polyfill URL.parse for Chrome <129 compatibility

frontend/src/main.tsx

@@ -1,3 +1,11 @@
+// Polyfill URL.parse for browsers that don't support it (Chrome <129, Firefox <135, Safari <18.2)
+// Required by pdfjs-dist 5.x which uses this API in production builds
+if (!('parse' in URL)) {
+  ;(URL as any).parse = (url: string, base?: string) => {
+    try { return new URL(url, base) } catch { return null }
+  }
+}
+
 import React from 'react'
 import { createRoot } from 'react-dom/client'
 import App from './App'