feat(vocabLesson): enhance input handling for gap-fill exercises

- Added functionality to manage Enter key events for gap-fill and single input fields, improving user experience during exercises.
- Introduced methods `onGapInputEnter` and `onSingleInputEnter` to streamline answer checking and navigation between input fields.
- Updated input elements with refs for better focus management, ensuring a smoother interaction flow for users.

frontend/src/views/social/VocabLessonView.vue

@@ -613,6 +613,8 @@
                 v-model="exerciseAnswers[exercise.id][index]"
                 :placeholder="$t('socialnetwork.vocab.courses.enterAnswer')"
                 class="gap-input"
+                :ref="getGapInputRef(exercise.id, index)"
+                @keydown.enter.prevent="onGapInputEnter(exercise, index)"
               />
             </div>
             <button @click="checkAnswer(exercise.id)" :disabled="!hasAllGapsFilled(exercise)">
@@ -637,6 +639,8 @@
               v-model="exerciseAnswers[exercise.id]" 
               :placeholder="$t('socialnetwork.vocab.courses.enterAnswer')"
               class="transformation-input"
+              :ref="'exercise-input-' + exercise.id"
+              @keydown.enter.prevent="onSingleInputEnter(exercise)"
             />
             <button @click="checkAnswer(exercise.id)" :disabled="!exerciseAnswers[exercise.id]">
               {{ $t('socialnetwork.vocab.courses.checkAnswer') }}
@@ -662,6 +666,8 @@
               v-model="exerciseAnswers[exercise.id]"
               :placeholder="$t('socialnetwork.vocab.courses.buildSentencePlaceholder')"
               class="transformation-input"
+              :ref="'exercise-input-' + exercise.id"
+              @keydown.enter.prevent="onSingleInputEnter(exercise)"
             />
             <button @click="checkAnswer(exercise.id)" :disabled="!exerciseAnswers[exercise.id]">
               {{ $t('socialnetwork.vocab.courses.checkAnswer') }}
@@ -684,6 +690,8 @@
               v-model="exerciseAnswers[exercise.id]"
               :placeholder="$t('socialnetwork.vocab.courses.completeDialogPlaceholder')"
               class="transformation-input"
+              :ref="'exercise-input-' + exercise.id"
+              @keydown.enter.prevent="onSingleInputEnter(exercise)"
             />
             <button @click="checkAnswer(exercise.id)" :disabled="!exerciseAnswers[exercise.id]">
               {{ $t('socialnetwork.vocab.courses.checkAnswer') }}
@@ -2854,6 +2862,30 @@ export default {
       const matches = qData.text?.match(/\{gap\}/g);
       return matches ? matches.length : (qData.gaps || 1);
     },
+    getGapInputRef(exerciseId, index) {
+      return `gap-input-${exerciseId}-${index}`;
+    },
+    onGapInputEnter(exercise, index) {
+      const gapCount = this.getGapCount(exercise);
+      // Bei mehreren Feldern: Enter springt weiter, beim letzten wird geprüft
+      if (gapCount > 1 && index < gapCount - 1) {
+        const nextRefKey = this.getGapInputRef(exercise.id, index + 1);
+        const nextRef = this.$refs[nextRefKey];
+        if (nextRef && nextRef.focus) {
+          nextRef.focus();
+        }
+        return;
+      }
+      // Letztes Feld (oder nur ein Feld): Antwort prüfen auslösen
+      this.checkAnswer(exercise.id);
+    },
+    onSingleInputEnter(exercise) {
+      const answer = this.exerciseAnswers[exercise.id];
+      if (!answer || (typeof answer === 'string' && !answer.trim())) {
+        return;
+      }
+      this.checkAnswer(exercise.id);
+    },
     hasAllGapsFilled(exercise) {
       const answers = this.exerciseAnswers[exercise.id];
       if (!answers || !Array.isArray(answers)) return false;