feat(tournament): improve result handling and display for matches and participants

backend/services/tournamentService.js

@@ -1452,7 +1452,8 @@ class TournamentService {
                         );
                         
                         if (!pairing1Key || !pairing2Key) continue;
-                        
+                        // Ergebnis kann null/undefiniert oder in anderem Format sein -> defensiv prüfen
+                        if (!m.result || typeof m.result !== 'string' || !m.result.includes(':')) continue;
                         const [s1, s2] = m.result.split(':').map(n => parseInt(n, 10));
                         
                         if (s1 > s2) {