Enhance logging and conditional rendering in VocabService and VocabLessonView

- Added detailed logging in VocabService for lesson retrieval, including lesson ID, title, and exercise count.
- Improved conditional rendering in VocabLessonView to handle cases where grammar exercises may not be present, enhancing user experience.
- Updated logging in VocabLessonView to provide insights into loaded lessons and exercises, aiding in debugging and monitoring.

check-lesson-exercises.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+# Script zum Prüfen, ob Übungen für eine Lektion vorhanden sind
+# Verwendung: ./check-lesson-exercises.sh [lesson_id]
+
+LESSON_ID="${1:-1}"
+
+echo "🔍 Prüfe Übungen für Lektion ID: $LESSON_ID"
+echo ""
+
+psql -U yourpart -d yp3 << EOF
+-- Prüfe Lektion
+SELECT 
+    l.id,
+    l.title,
+    l.course_id,
+    COUNT(e.id) as exercise_count
+FROM community.vocab_course_lesson l
+LEFT JOIN community.vocab_grammar_exercise e ON e.lesson_id = l.id
+WHERE l.id = $LESSON_ID
+GROUP BY l.id, l.title, l.course_id;
+
+-- Zeige alle Übungen für diese Lektion
+SELECT 
+    e.id,
+    e.exercise_number,
+    e.title,
+    e.exercise_type_id,
+    et.name as exercise_type_name
+FROM community.vocab_grammar_exercise e
+LEFT JOIN community.vocab_grammar_exercise_type et ON et.id = e.exercise_type_id
+WHERE e.lesson_id = $LESSON_ID
+ORDER BY e.exercise_number;
+EOF