fix: reseed sets createdAt from filename timestamp or file mtime

Photos reseeded from disk now sort by their original upload time
instead of all getting the same insertion timestamp.

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

main-site/photo-gallery-app/backend/scripts/reseed_uploads.js

@@ -48,11 +48,17 @@ async function main() {
         const baseName = path.basename(file, path.extname(file));
         const caption = baseName.replace(/[-_]+/g, ' ');
         const tag = baseName.split('-')[1] || 'uncategorized';
+        const tsMatch = file.match(/^(\d{13})-/);
+        const createdAt = tsMatch
+            ? new Date(parseInt(tsMatch[1]))
+            : fs.statSync(path.join(UPLOAD_DIR, file)).mtime;
         const doc = new Photo({
             filename: file,
             path: path.join('uploads', file),
             caption,
             tags: [tag],
+            createdAt,
+            updatedAt: createdAt,
         });
         await doc.save();
         created++;