"Update backend configuration and tests for improved stability"

backend/app.py

@@ -90,6 +90,18 @@ def create_app(config_name=None):
     # Hintergrund-Tasks registrieren
     register_background_tasks(app)
     
+    # Parse PRINTERS als JSON
+    printers_env = app.config.get('PRINTERS', '{}')
+    if isinstance(printers_env, str):
+        try:
+            app.config['PRINTERS'] = json.loads(printers_env)
+        except (json.JSONDecodeError, TypeError):
+            app.config['PRINTERS'] = {}
+    elif isinstance(printers_env, dict):
+        app.config['PRINTERS'] = printers_env
+    else:
+        app.config['PRINTERS'] = {}
+    
     return app
 
 # Initialisierung - wird später durch create_app ersetzt
@@ -1943,4 +1955,16 @@ else:
         printers_config = json.loads(app.config.get('PRINTERS', '{}'))
         if printers_config:
             init_printers()
-        setup_frontend_v2()
+        setup_frontend_v2()
+
+    # Parse PRINTERS als JSON
+    printers_env = app.config.get('PRINTERS', '{}')
+    if isinstance(printers_env, str):
+        try:
+            app.config['PRINTERS'] = json.loads(printers_env)
+        except (json.JSONDecodeError, TypeError):
+            app.config['PRINTERS'] = {}
+    elif isinstance(printers_env, dict):
+        app.config['PRINTERS'] = printers_env
+    else:
+        app.config['PRINTERS'] = {}