Enhance member gallery generation to support JSON format without image creation

This commit updates the member gallery generation functionality to allow returning a list of members in JSON format without creating images. The `generateMemberGallery` method in the MemberService is modified to accept a new parameter, `createImage`, which determines whether images should be generated. This change improves the flexibility of the API for different use cases.

backend/controllers/memberController.js

@@ -131,10 +131,14 @@ const generateMemberGallery = async (req, res) => {
         const { authcode: userToken } = req.headers;
         const size = parseInt(req.query.size) || 200; // Default: 200x200
         const format = req.query.format || 'image'; // 'image' or 'json'
-        const result = await MemberService.generateMemberGallery(userToken, clubId, size);
+        
+        // Bei format=json wird kein Bild erstellt, nur die Mitgliederliste zurückgegeben
+        const createImage = format !== 'json';
+        const result = await MemberService.generateMemberGallery(userToken, clubId, size, createImage);
+        
         if (result.status === 200) {
             if (format === 'json') {
-                // Return member information for interactive gallery
+                // Return member information for interactive gallery (ohne Bild zu erstellen)
                 return res.status(200).json({
                     members: result.galleryEntries.map(entry => ({
                         memberId: entry.memberId,