feat(TournamentTab): improve knockout section handling and data validation

- Refactored stages and advancements data retrieval to ensure proper handling of empty or invalid responses.
- Added scrollToKnockoutSection method to enhance user experience by automatically scrolling to the knockout section after initiating tournament actions.
- Updated knockout operation flow to include scrolling behavior, ensuring better visibility of the knockout stage during tournament management.

frontend/src/views/TournamentTab.vue

@@ -2644,8 +2644,9 @@ export default {
                         }
                     });
 
-                    const stages = stagesRes?.data?.stages;
-                    if (Array.isArray(stages) && stages.length > 0) {
+                    const stages = Array.isArray(stagesRes?.data?.stages) ? stagesRes.data.stages : [];
+                    const advancements = Array.isArray(stagesRes?.data?.advancements) ? stagesRes.data.advancements : [];
+                    if (stages.length > 0 && advancements.length > 0) {
                         const normalizedStages = stages
                             .map(s => ({
                                 ...s,
@@ -2680,6 +2681,7 @@ export default {
 
                                 if ((stage.type || stage.targetType || stage.target) === 'knockout') {
                                     await this.loadTournamentData();
+                                    await this.scrollToKnockoutSection();
                                     return;
                                 }
 
@@ -2696,6 +2698,7 @@ export default {
                     tournamentId: this.selectedDate
                 });
                 await this.loadTournamentData();
+                await this.scrollToKnockoutSection();
             } catch (error) {
                 console.error('Fehler beim Starten der K.o.-Runde:', error);
                 await this.showInfo(
@@ -2708,6 +2711,21 @@ export default {
                 this.knockoutOperationInProgress = false;
             }
         },
+        async scrollToKnockoutSection() {
+            await this.$nextTick();
+            window.setTimeout(() => {
+                const knockoutSection = document.querySelector('.ko-round');
+                if (knockoutSection && typeof knockoutSection.scrollIntoView === 'function') {
+                    knockoutSection.scrollIntoView({ behavior: 'smooth', block: 'start' });
+                    return;
+                }
+
+                const placementsSection = document.querySelector('.ranking');
+                if (placementsSection && typeof placementsSection.scrollIntoView === 'function') {
+                    placementsSection.scrollIntoView({ behavior: 'smooth', block: 'start' });
+                }
+            }, 120);
+        },
 
         formatResult(match) {
             if (!match.tournamentResults?.length) return '-';