fix: harden school imports and add optional feedback diagnostics

mobile/lib/domain/exam_schedule.dart

@@ -46,6 +46,10 @@ class ExamRecord {
       return value;
     }
 
+    final typeId = json['examTypeId'];
+    if (typeId != null && (typeId is! int || typeId < 1 || typeId > 3)) {
+      throw const FormatException('考试类型无效');
+    }
     final record = ExamRecord(
       code: field('code'),
       name: field('name'),
@@ -58,7 +62,7 @@ class ExamRecord {
       date: field('date', optional: true),
       status: field('status', optional: true),
       notes: field('notes', optional: true),
-      examTypeId: json['examTypeId'] as int?,
+      examTypeId: typeId as int?,
     );
     if (record.code.isEmpty || record.name.isEmpty) {
       throw const FormatException('考试课程无效');
@@ -107,7 +111,8 @@ class ExamSchedule {
           ? SupportedSchool.uestcGraduate
           : SupportedSchool.fromId(json['schoolId'] as String);
       final rawTypes = json['requestedExamTypes'] ?? <int>[];
-      if (rawTypes is! List || rawTypes.any((t) => t is! int || t < 1 || t > 3)) {
+      if (rawTypes is! List ||
+          rawTypes.any((t) => t is! int || t < 1 || t > 3)) {
         throw const FormatException('考试类型无效');
       }
       final types = rawTypes.cast<int>().toSet();