fix: no-cache headers on config+download endpoints, cache-bust config fetch from frontend

renderer/onlyoffice-service.js

@@ -135,6 +135,11 @@ router.get('/:templateId/config', (req, res) => {
     return res.status(404).json({ error: 'Template file missing' });
   }
   
+  // Prevent browser caching of the config — always return fresh config
+  res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate');
+  res.setHeader('Pragma', 'no-cache');
+  res.setHeader('Expires', '0');
+  
   // Get file modification time for cache-busting doc key
   const fileStats = fs.statSync(template.path);
   const fileMtime = fileStats.mtimeMs;
@@ -235,6 +240,9 @@ router.get('/:templateId/download', (req, res) => {
   const fileName = template.originalName || template.name + '.docx';
   res.setHeader('Content-Type', 'application/vnd.openxmlformats-officedocument.wordprocessingml.document');
   res.setHeader('Content-Disposition', `attachment; filename="${fileName}"`);
+  res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate');
+  res.setHeader('Pragma', 'no-cache');
+  res.setHeader('Expires', '0');
   
   const fileStream = fs.createReadStream(template.path);
   fileStream.pipe(res);