added guardian login with views for their assigned childs

lib/session/session_lifecycle.dart

@@ -0,0 +1,25 @@
+import 'dart:developer';
+
+import '../api/marianumconnect/queries/auth_logout/auth_logout.dart';
+import '../auth_link/guardian_link_listener.dart';
+import '../push/push_registration.dart';
+import 'session_manager.dart';
+
+abstract final class SessionLifecycle {
+  /// Ordered teardown: unregister push and revoke the Nextcloud app passwords
+  /// (while those credentials still exist), then revoke the MC bearer token,
+  /// finally wipe the local session. Each step is best-effort so an offline
+  /// sign-out still reaches a clean local state.
+  static Future<void> signOut() async {
+    try {
+      await PushRegistration().logoutCleanup();
+    } on Object catch (e) {
+      log('Sign-out: push cleanup failed: $e');
+    }
+    await AuthLogout().run();
+    await SessionManager().signOut();
+    // A login link that arrived while signed in must not be replayed on the
+    // login screen that follows.
+    GuardianLinkListener.clear();
+  }
+}