refactor(sentry): standardize exceptions to prevent Sentry minification

integration_test/exceptions/mailbox/null_inbox_unread_count_exception.dart

@@ -1 +1,8 @@
-class NullInboxUnreadCountException implements Exception {}
+import 'package:core/domain/exceptions/app_base_exception.dart';
+
+class NullInboxUnreadCountException extends AppBaseException {
+  const NullInboxUnreadCountException([super.message]);
+
+  @override
+  String get exceptionName => 'NullInboxUnreadCountException';
+}

integration_test/exceptions/mailbox/null_quota_exception.dart

@@ -1 +1,8 @@
-class NullQuotaException implements Exception {}
+import 'package:core/domain/exceptions/app_base_exception.dart';
+
+class NullQuotaException extends AppBaseException {
+  NullQuotaException([super.message]);
+
+  @override
+  String get exceptionName => 'NullQuotaException';
+}