fix(DiaryView): improve drag-and-drop item reordering logic

- Updated the drag-and-drop functionality to correctly handle item indices during reordering, ensuring accurate updates to the training plan.
- Enhanced error handling by loading the training plan after a successful reorder, improving user experience and stability.

frontend/src/views/DiaryView.vue

@@ -2242,15 +2242,17 @@ export default {
             }
         },
         async onDragEnd(evt) {
-            const movedItem = this.trainingPlan[evt.oldIndex];
+            const oldIndex = Number.isInteger(evt.oldDraggableIndex) ? evt.oldDraggableIndex : evt.oldIndex;
+            const newIndex = Number.isInteger(evt.newDraggableIndex) ? evt.newDraggableIndex : evt.newIndex;
+            const movedItem = this.trainingPlan[oldIndex];
             if (!movedItem) {
                 return;
             }
             try {
                 await apiClient.put(`/diary-date-activities/${this.currentClub}/${movedItem.id}/order`, {
-                    orderId: evt.newIndex
+                    orderId: newIndex + 1
                 });
-                this.recalculateTimes();
+                await this.loadTrainingPlan();
             } catch (error) {
                 this.showInfo(this.$t('messages.error'), this.$t('diary.errorOccurred'), '', 'error');
             }