Refactor schedule view to improve PDF generation and enhance element referencing

Updated ScheduleView.vue to replace direct DOM querying with Vue's ref system for better maintainability. The 'flex-item' div now uses a reference for PDF generation, improving code clarity and performance. This change aligns with best practices in Vue component design.

frontend/src/views/ScheduleView.vue

@@ -20,7 +20,7 @@
                 <li v-if="leagues.length === 0" class="no-leagues">Keine Ligen für diese Saison gefunden</li>
             </ul>
             
-            <div class="flex-item">
+            <div class="flex-item" ref="scheduleContainer">
                 <!-- Tab Navigation - nur anzeigen wenn Liga ausgewählt -->
                 <div v-if="selectedLeague && selectedLeague !== ''" class="tab-navigation">
                     <button 
@@ -625,7 +625,7 @@ export default {
             return club ? club.name : '';
         },
         async generatePDF() {
-            const element = this.$el.querySelector('.flex-item > div');
+            const element = this.$refs.scheduleContainer;
             const highlightName = this.getCurrentClubName();
             if (element) {
                 const pdfGen = new PDFGenerator();