Fix standalone TTR preview route without saved match ID

backend/controllers/matchController.js

@@ -247,3 +247,9 @@ export const getTtrPreviewPlayers = async (req, res) => {
         return res.status(error.statusCode || 500).json({ error: error.message || 'TTR-Werte konnten nicht geladen werden' });
     }
 };
+
+export const getStandaloneTtrPreviewPlayers = async (req, res) => {
+    // The literal /ttr-preview/standalone route has no :matchId parameter.
+    req.params.matchId = 'standalone';
+    return getTtrPreviewPlayers(req, res);
+};