PDF preview: thumbnails via Ghostscript, preview in file cards

- GET /pdf/preview/:fileId — renders first page as PNG (72 DPI)
- GET /pdf/preview/:fileId/:page — specific page preview
- GET /pdf/thumbnails/:fileId — list of all page preview URLs
- File cards show actual PDF thumbnail instead of icon
- Cached previews (30 min cleanup)
- Fallback to PDF icon if preview fails

public/pdf.html

@@ -147,6 +147,19 @@
         .file-card-icon {
             flex-shrink: 0;
             color: var(--accent);
+            width: 48px;
+            height: 48px;
+            border-radius: 6px;
+            overflow: hidden;
+            display: flex;
+            align-items: center;
+            justify-content: center;
+            background: var(--surface-600);
+        }
+        .file-card-icon img {
+            width: 100%;
+            height: 100%;
+            object-fit: cover;
         }
         .file-card-info {
             flex: 1;
@@ -1071,7 +1084,7 @@
             card.dataset.id = f.id;
             card.innerHTML = `
                 <div class="file-card-order">${idx + 1}</div>
-                <div class="file-card-icon">${pdfIcon(20)}</div>
+                <div class="file-card-icon"><img src="/pdf/preview/${f.id}" alt="" onerror="this.parentNode.innerHTML=pdfIcon(20)"></div>
                 <div class="file-card-info">
                     <div class="file-card-name">${escHtml(f.name)}</div>
                     <div class="file-card-meta">${formatSize(f.size)} · ${f.pages} стр.</div>

routes/pdf.js

@@ -101,6 +101,55 @@ router.post('/upload', limiter, upload.array('files', 10), async (req, res) => {
   res.json({ files: results });
 });
 
+// Preview — render PDF page as PNG thumbnail via Ghostscript
+router.get('/preview/:fileId', (req, res) => renderPreview(req, res, 1));
+router.get('/preview/:fileId/:page', (req, res) => renderPreview(req, res, parseInt(req.params.page) || 1));
+
+async function renderPreview(req, res, pageNum) {
+  const f = getFile(req.params.fileId);
+  if (!f) return res.status(404).json({ error: 'Файл не найден' });
+
+  const cacheKey = `${f.id}_p${pageNum}`;
+  const cachePath = path.join(DOWNLOADS_DIR, `preview_${cacheKey}.png`);
+
+  // Return cached if exists
+  if (fs.existsSync(cachePath)) {
+    return res.type('png').sendFile(cachePath);
+  }
+
+  try {
+    await new Promise((resolve, reject) => {
+      const proc = spawn('gs', [
+        '-sDEVICE=png16m', '-r72', '-dNOPAUSE', '-dBATCH', '-dQUIET',
+        `-dFirstPage=${pageNum}`, `-dLastPage=${pageNum}`,
+        '-dTextAlphaBits=4', '-dGraphicsAlphaBits=4',
+        `-sOutputFile=${cachePath}`, f.path,
+      ], { timeout: 15000 });
+      proc.on('close', code => code === 0 ? resolve() : reject(new Error('Preview failed')));
+      proc.on('error', reject);
+    });
+
+    // Cleanup after 30 min
+    setTimeout(() => { try { fs.unlinkSync(cachePath); } catch {} }, 30 * 60 * 1000);
+
+    res.type('png').sendFile(cachePath);
+  } catch (err) {
+    res.status(500).json({ error: 'Не удалось создать превью' });
+  }
+}
+
+// Thumbnails — return preview URLs for all pages
+router.get('/thumbnails/:fileId', async (req, res) => {
+  const f = getFile(req.params.fileId);
+  if (!f) return res.status(404).json({ error: 'Файл не найден' });
+
+  const urls = [];
+  for (let i = 1; i <= Math.min(f.pages, 50); i++) {
+    urls.push(`/pdf/preview/${f.id}/${i}`);
+  }
+  res.json({ pages: f.pages, thumbnails: urls });
+});
+
 // Info
 router.get('/info/:fileId', async (req, res) => {
   const f = getFile(req.params.fileId);