Enhance error handling in MyTischtennisUrlController and update TrainingStatsView with TTR and QTTR columns

Improved error handling in MyTischtennisUrlController by adding detailed debug information in the response, including status codes and relevant data. Updated TrainingStatsView to display TTR and QTTR values for members, enhancing data visibility and user experience.

frontend/src/views/TrainingStatsView.vue

@@ -76,6 +76,8 @@
                 <span class="sort-icon">{{ getSortIcon('name') }}</span>
               </div>
             </th>
+            <th>TTR</th>
+            <th>QTTR</th>
             <th>Geburtsdatum</th>
             <th @click="sortBy('participation12Months')" class="sortable-header">
               <div class="header-content">
@@ -107,6 +109,8 @@
         <tbody>
           <tr v-for="member in sortedMembers" :key="member.id" class="member-row">
             <td>{{ member.firstName }} {{ member.lastName }}</td>
+            <td>{{ member.ttr ?? '–' }}</td>
+            <td>{{ member.qttr ?? '–' }}</td>
             <td>{{ formatBirthdate(member.birthDate) }}</td>
             <td>{{ member.participation12Months }}</td>
             <td>{{ member.participation3Months }}</td>