added guardian login with views for their assigned childs

lib/auth_link/pending_guardian_request.dart

@@ -0,0 +1,83 @@
+import 'dart:convert';
+
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+
+/// A guardian login request waiting for its code or link. Persisted because
+/// Android often kills the app while the user reads the mail.
+class PendingGuardianRequest {
+  static const int defaultCodeLength = 6;
+
+  final String requestId;
+  final String email;
+  final String deviceSecret;
+  final DateTime expiresAt;
+  final DateTime resendAvailableAt;
+  final int codeLength;
+
+  const PendingGuardianRequest({
+    required this.requestId,
+    required this.email,
+    required this.deviceSecret,
+    required this.expiresAt,
+    required this.resendAvailableAt,
+    this.codeLength = defaultCodeLength,
+  });
+
+  bool isExpired(DateTime now) => !now.isBefore(expiresAt);
+
+  Map<String, Object> toJson() => {
+    'requestId': requestId,
+    'email': email,
+    'deviceSecret': deviceSecret,
+    'expiresAt': expiresAt.toIso8601String(),
+    'resendAvailableAt': resendAvailableAt.toIso8601String(),
+    'codeLength': codeLength,
+  };
+
+  static PendingGuardianRequest? fromJson(Map<String, dynamic> json) {
+    try {
+      return PendingGuardianRequest(
+        requestId: json['requestId'] as String,
+        email: json['email'] as String,
+        deviceSecret: json['deviceSecret'] as String,
+        expiresAt: DateTime.parse(json['expiresAt'] as String),
+        resendAvailableAt: DateTime.parse(json['resendAvailableAt'] as String),
+        codeLength: json['codeLength'] as int? ?? defaultCodeLength,
+      );
+    } on Object {
+      return null;
+    }
+  }
+}
+
+class PendingGuardianRequestStore {
+  static const _key = 'guardian_login_pending_request';
+  static const FlutterSecureStorage _storage = FlutterSecureStorage(
+    iOptions: IOSOptions(accessibility: KeychainAccessibility.first_unlock),
+  );
+
+  const PendingGuardianRequestStore();
+
+  Future<PendingGuardianRequest?> read() async {
+    try {
+      final raw = await _storage.read(key: _key);
+      if (raw == null) return null;
+      return PendingGuardianRequest.fromJson(
+        jsonDecode(raw) as Map<String, dynamic>,
+      );
+    } on Object {
+      return null;
+    }
+  }
+
+  Future<void> write(PendingGuardianRequest request) =>
+      _storage.write(key: _key, value: jsonEncode(request.toJson()));
+
+  Future<void> clear() async {
+    try {
+      await _storage.delete(key: _key);
+    } on Object {
+      // Nothing stored or keystore unavailable.
+    }
+  }
+}