Render document content inline instead of in iframe

Replace the <iframe> with an inline <div> containing the mammoth HTML.
Content now flows full-width with the page instead of being cramped in
a fixed-height scrolling box. Download link still available below.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server.js

@@ -1548,22 +1548,16 @@ app.post('/api/admin/upload-attachment', requirePin, async (req, res) => {
     return res.status(500).json({ error: `Could not save file: ${err.message}` });
   }
 
-  // Convert to HTML so it can be shown in an iframe
-  let htmlUrl = null;
+  // Convert to HTML for inline rendering
+  let htmlBody = null;
   try {
-    const { value: bodyHtml } = await mammoth.convertToHtml({ buffer });
-    const htmlFilename = `${uuid}.html`;
-    const page = `<!doctype html><html><head><meta charset="utf-8">
-<style>body{font-family:sans-serif;max-width:800px;margin:2rem auto;padding:0 1rem;line-height:1.6}
-img{max-width:100%}table{border-collapse:collapse;width:100%}td,th{border:1px solid #ccc;padding:.4em .6em}</style>
-</head><body>${bodyHtml}</body></html>`;
-    await writeFile(join(ATTACHMENTS_DIR, htmlFilename), page);
-    htmlUrl = `/api/attachments/${htmlFilename}`;
+    const { value } = await mammoth.convertToHtml({ buffer });
+    htmlBody = value || null;
   } catch (_) {
-    // HTML preview generation failed — download link still works
+    // preview failed — download link still works
   }
 
-  return res.json({ url: `/api/attachments/${filename}`, htmlUrl, originalName });
+  return res.json({ url: `/api/attachments/${filename}`, htmlBody, originalName });
 });
 
 app.get('/health', (req, res) => res.json({ ok: true }));