Fix: Lazy initialization of services to prevent empty lessons list

Problem:
- Blueprints were imported BEFORE lessons were loaded
- routes/training.py imported 'lessons' when it was still empty []
- This caused "Lektion nicht gefunden" / "Unbekannte Lektion"

Solution:
- Changed to import entire 'helpers' module instead of 'lessons'
- Implemented lazy initialization with get_services()
- Services are created on first route access AFTER lessons are loaded
- Updated all route handlers to use get_services()

This fixes the timing issue between blueprint imports and lesson loading.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

routes/training.py

@@ -6,7 +6,7 @@ Handles all training-related routes
 import logging
 from flask import Blueprint, render_template, request, jsonify
 from models import db
-from services.helpers import lessons
+from services import helpers
 from services.lesson_service import LessonService
 from services.training_service import TrainingService
 
@@ -14,15 +14,25 @@ logger = logging.getLogger(__name__)
 
 training_bp = Blueprint('training', __name__)
 
-# Initialize services
-lesson_service = LessonService(lessons)
-training_service = TrainingService(lesson_service)
+# Initialize services (will be populated when lessons are loaded)
+lesson_service = None
+training_service = None
+
+
+def get_services():
+    """Lazy initialization of services after lessons are loaded"""
+    global lesson_service, training_service
+    if lesson_service is None:
+        lesson_service = LessonService(helpers.lessons)
+        training_service = TrainingService(lesson_service)
+    return lesson_service, training_service
 
 
 @training_bp.route('/train')
 def train():
     """Hauptseite des Tipptrainers"""
     try:
+        _, training_service = get_services()
         context = training_service.get_training_context()
         return render_template('index.html', **context)
 
@@ -72,6 +82,7 @@ def update_progress():
 
         try:
             # Update progress and get statistics
+            _, training_service = get_services()
             stats = training_service.update_training_progress(
                 user_input=user_input,
                 current_text=current_text,
@@ -99,6 +110,7 @@ def update_progress():
 def next_text():
     """Wechselt zum nächsten Text"""
     try:
+        _, training_service = get_services()
         result = training_service.switch_to_next_lesson()
         return jsonify(result)
 
@@ -117,6 +129,7 @@ def set_lesson():
         if lesson_index is None or not isinstance(lesson_index, int):
             return jsonify({'error': 'Ungültiger Lektionsindex'}), 400
 
+        _, training_service = get_services()
         success, result = training_service.switch_to_lesson(lesson_index)
 
         if not success:
@@ -154,7 +167,7 @@ def save_lesson_statistics():
             return jsonify({'error': 'Ungültige Datentypen'}), 400
 
         # Bereichsvalidierung
-        if lesson_index < 0 or lesson_index >= len(lessons):
+        if lesson_index < 0 or lesson_index >= len(helpers.lessons):
             return jsonify({'error': 'Ungültiger Lektionsindex'}), 400
 
         if chars_per_minute < 0 or error_rate < 0 or wpm < 0 or training_duration < 0:
@@ -188,6 +201,7 @@ def save_lesson_statistics():
 def reset_lesson():
     """Setzt den Fortschritt der aktuellen Lektion zurück"""
     try:
+        _, training_service = get_services()
         success, result = training_service.reset_current_lesson()
 
         if not success: