fix: Add explicit Content-Type and Content-Disposition headers for downloads

Improves browser compatibility for PDF file downloads by setting
proper MIME type and filename encoding.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/controllers/ai-kurzy.controller.js

@@ -247,6 +247,11 @@ export const downloadPriloha = async (req, res, next) => {
       return res.status(404).json({ success: false, error: { message: 'Súbor nenájdený na serveri' } });
     }
 
+    // Set explicit headers for better browser compatibility
+    const mimeType = priloha.mimeType || 'application/octet-stream';
+    res.setHeader('Content-Type', mimeType);
+    res.setHeader('Content-Disposition', `attachment; filename="${encodeURIComponent(priloha.nazovSuboru)}"`);
+
     res.download(priloha.cestaKSuboru, priloha.nazovSuboru);
   } catch (error) {
     next(error);