Redesign document workspace layout and tighten frontend type config

frontend/src/components/DocumentCard.tsx

@@ -2,6 +2,7 @@
  * Card view for displaying document summary, preview, and metadata.
  */
 import { useState } from 'react';
+import type { JSX } from 'react';
 import { Download, FileText, Trash2 } from 'lucide-react';
 
 import type { DmsDocument } from '../types';