Add PDF first-page thumbnails via pdftoppm

Generated at upload time, stored alongside the PDF in data/pdfs/.
Shown in the file picker (48px) and component detail view (80px).
Gracefully skipped if pdftoppm is unavailable.

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

server.mjs

@@ -5,6 +5,7 @@ import express from 'express';
 import multer from 'multer';
 import { unlinkSync, mkdirSync } from 'node:fs';
 import { extname, join } from 'node:path';
+import { execFileSync } from 'node:child_process';
 import sharp from 'sharp';
 import { generate_id } from './lib/ids.mjs';
 import { compute_cell_size, process_grid_image } from './lib/grid-image.mjs';
@@ -62,6 +63,20 @@ function remove_image_file(img_id) {
 	try { unlinkSync(join('./data/images', img_id)); } catch {}
 }
 
+function generate_pdf_thumb(pdf_path, thumb_prefix) {
+	// Returns thumb filename (id-thumb.png) on success, null if pdftoppm unavailable.
+	try {
+		execFileSync('pdftoppm', [
+			'-png', '-singlefile', '-scale-to', '512',
+			'-f', '1', '-l', '1',
+			pdf_path, thumb_prefix,
+		]);
+		return thumb_prefix.split('/').pop() + '.png';
+	} catch {
+		return null;
+	}
+}
+
 // ---------------------------------------------------------------------------
 // Field definitions
 // ---------------------------------------------------------------------------
@@ -491,12 +506,16 @@ app.post('/api/pdfs', pdf_upload.single('file'), (req, res) => {
 		try { unlinkSync(join('./data/pdfs', req.file.filename)); } catch {}
 		return fail(res, 'a file with that name already exists');
 	}
+	const id = generate_id();
+	const thumb_prefix = join('./data/pdfs', id + '-thumb');
+	const thumb_file = generate_pdf_thumb(join('./data/pdfs', req.file.filename), thumb_prefix);
 	const pdf = {
-		id: generate_id(),
+		id,
 		filename: req.file.filename,
 		display_name,
 		original_name: req.file.originalname,
 		size: req.file.size,
+		thumb_filename: thumb_file,
 		uploaded_at: Date.now(),
 	};
 	set_pdf(pdf);
@@ -520,6 +539,7 @@ app.delete('/api/pdfs/:id', (req, res) => {
 	const pdf = get_pdf(req.params.id);
 	if (!pdf) return fail(res, 'not found', 404);
 	try { unlinkSync(join('./data/pdfs', pdf.filename)); } catch {}
+	if (pdf.thumb_filename) { try { unlinkSync(join('./data/pdfs', pdf.thumb_filename)); } catch {} }
 	delete_pdf(req.params.id);
 	ok(res);
 });