added guardian login with views for their assigned childs

lib/api/demo/demo_mode.dart

@@ -1,4 +1,4 @@
-import '../../model/account_data.dart';
+import '../../session/session_manager.dart';
 
 /// Central switch for the client-side demo mode.
 ///
@@ -8,7 +8,7 @@ import '../../model/account_data.dart';
 /// Play reviewers and automated screenshot runs see a fully populated app
 /// without a real account and without any network dependency.
 ///
-/// The flag is persisted through [AccountData.isDemo], so a demo session
+/// The flag is persisted through [Session.isDemo], so a demo session
 /// survives cold starts exactly like a normal login. It works in release builds
 /// too — reviewers run the shipped release build.
 class DemoMode {
@@ -22,6 +22,14 @@ class DemoMode {
   static bool matches(String username) =>
       username.trim().toLowerCase().startsWith(usernamePrefix);
 
+  /// Guardian logins are passwordless, so reviewers need a fixed address that
+  /// skips the mail round-trip. Deliberately not the `demo@` prefix, which a
+  /// real e-mail address could start with.
+  static const String guardianEmail = 'demo-eltern@marianum-fulda.de';
+
+  static bool matchesGuardian(String email) =>
+      email.trim().toLowerCase() == guardianEmail;
+
   /// True while the active session is a demo session.
-  static bool get active => AccountData().isDemo;
+  static bool get active => SessionManager().isDemo;
 }