Enhance survival sentences exercises and VocabCourseView for improved user experience

- Added multiple choice exercises for common phrases in Bisaya, including questions and explanations to aid learning.
- Introduced a gap fill exercise for completing survival sentences, enhancing interactive learning.
- Updated VocabCourseView to display a button for continuing the current lesson, ensuring smoother navigation.
- Implemented logic to prevent starting lessons without completing previous ones, improving course progression management.

frontend/src/views/social/VocabCourseView.vue

@@ -19,6 +19,11 @@
       </div>
 
       <div v-if="course.lessons && course.lessons.length > 0" class="lessons-list">
+        <div class="current-lesson-section" v-if="currentLesson">
+          <button @click="openLesson(currentLesson.id)" class="btn-current-lesson">
+            {{ $t('socialnetwork.vocab.courses.continueCurrentLesson') }}
+          </button>
+        </div>
         <h3>{{ $t('socialnetwork.vocab.courses.lessons') }}</h3>
         <table class="lessons-table">
           <thead>
@@ -53,7 +58,12 @@
               </td>
               <td class="lesson-actions">
                 <div class="lesson-actions-content">
-                  <button @click="openLesson(lesson.id)" class="btn-start">
+                  <button 
+                    @click="openLesson(lesson.id)" 
+                    class="btn-start"
+                    :disabled="!canStartLesson(lesson)"
+                    :title="!canStartLesson(lesson) ? $t('socialnetwork.vocab.courses.previousLessonRequired') : ''"
+                  >
                     {{ getLessonProgress(lesson.id)?.completed ? $t('socialnetwork.vocab.courses.review') : $t('socialnetwork.vocab.courses.start') }}
                   </button>
                   <button v-if="isOwner" @click="editLesson(lesson.id)" class="btn-edit">{{ $t('socialnetwork.vocab.courses.edit') }}</button>
@@ -134,6 +144,25 @@ export default {
     ...mapGetters(['user']),
     isOwner() {
       return this.course && this.course.ownerUserId === this.user?.id;
+    },
+    currentLesson() {
+      if (!this.course || !this.course.lessons || this.course.lessons.length === 0) {
+        return null;
+      }
+      
+      // Sortiere Lektionen nach lessonNumber
+      const sortedLessons = [...this.course.lessons].sort((a, b) => a.lessonNumber - b.lessonNumber);
+      
+      // Finde die erste nicht abgeschlossene Lektion
+      for (const lesson of sortedLessons) {
+        const progress = this.getLessonProgress(lesson.id);
+        if (!progress || !progress.completed) {
+          return lesson;
+        }
+      }
+      
+      // Alle Lektionen abgeschlossen - zeige die letzte Lektion
+      return sortedLessons[sortedLessons.length - 1];
     }
   },
   watch: {
@@ -177,6 +206,31 @@ export default {
     getLessonProgress(lessonId) {
       return this.progress.find(p => p.lessonId === lessonId);
     },
+    canStartLesson(lesson) {
+      if (!this.course || !this.course.lessons) {
+        return false;
+      }
+      
+      // Sortiere Lektionen nach lessonNumber
+      const sortedLessons = [...this.course.lessons].sort((a, b) => a.lessonNumber - b.lessonNumber);
+      
+      // Finde den Index der aktuellen Lektion
+      const currentIndex = sortedLessons.findIndex(l => l.id === lesson.id);
+      
+      // Die erste Lektion kann immer gestartet werden
+      if (currentIndex === 0) {
+        return true;
+      }
+      
+      // Wenn es nicht die erste Lektion ist, prüfe ob die vorherige abgeschlossen wurde
+      if (currentIndex > 0) {
+        const previousLesson = sortedLessons[currentIndex - 1];
+        const previousProgress = this.getLessonProgress(previousLesson.id);
+        return previousProgress && previousProgress.completed;
+      }
+      
+      return false;
+    },
     async addLesson() {
       try {
         await apiClient.post(`/api/vocab/courses/${this.courseId}/lessons`, this.newLesson);
@@ -256,6 +310,33 @@ export default {
   margin-top: 30px;
 }
 
+.current-lesson-section {
+  margin-bottom: 20px;
+  padding: 15px;
+  background: #f8f9fa;
+  border-radius: 8px;
+  display: flex;
+  justify-content: center;
+}
+
+.btn-current-lesson {
+  padding: 12px 24px;
+  background: #F9A22C;
+  color: #000000;
+  border: 1px solid #F9A22C;
+  border-radius: 4px;
+  cursor: pointer;
+  font-size: 1em;
+  font-weight: 600;
+  transition: background 0.05s;
+}
+
+.btn-current-lesson:hover {
+  background: #fdf1db;
+  color: #7E471B;
+  border: 1px solid #7E471B;
+}
+
 .lessons-table {
   width: 100%;
   border-collapse: separate;
@@ -420,12 +501,20 @@ export default {
   transition: background 0.05s;
 }
 
-.btn-start:hover {
+.btn-start:hover:not(:disabled) {
   background: #fdf1db;
   color: #7E471B;
   border: 1px solid #7E471B;
 }
 
+.btn-start:disabled {
+  background: #e0e0e0;
+  color: #999;
+  border: 1px solid #ccc;
+  cursor: not-allowed;
+  opacity: 0.6;
+}
+
 .btn-edit {
   padding: 6px 12px;
   background: #F9A22C;