Fix: Kassen ohne Passwort können nun wieder geöffnet werden

- Backend erkennt passwortlose Instanzen (Hash von leerem String)
- Login-Formular: required entfernt, Hinweis für passwortlose Kassen
- Bei leerem Feld und passwortloser Kasse wird Zugang gewährt

Made-with: Cursor

app.py

@@ -165,9 +165,21 @@ def admin(instance_id):
         
     auth_key = f'admin_auth_{instance_id}'
     
+    # Check if instance has no password (empty or None)
+    stored_password = instance['password']
+    has_no_password = (
+        stored_password is None or
+        check_password_hash(stored_password, '')
+    )
+
     # Handle Login Submission
     if request.method == "POST" and 'admin_password' in request.form:
-        if check_password_hash(instance['password'], request.form['admin_password']):
+        entered = request.form['admin_password']
+        if has_no_password and entered == '':
+            session[auth_key] = True
+            conn.close()
+            return redirect(url_for('admin', instance_id=instance_id))
+        elif not has_no_password and check_password_hash(stored_password, entered):
             session[auth_key] = True
             conn.close()
             return redirect(url_for('admin', instance_id=instance_id))