feat: keep undergraduate exams independent of course terms

mobile/lib/data/json_schedule_import.dart

@@ -1,5 +1,6 @@
 import '../domain/course.dart';
 import '../domain/school_term.dart';
+import '../domain/school_identity.dart';
 
 import 'dart:convert';
 
@@ -61,9 +62,31 @@ class JsonScheduleImport {
           ? SchoolTerm(int.parse(termIds.single))
           : null;
       if (termIds.length > 1 ||
-          (term != null && termIds.any((id) => id != term.id.toString()))) {
+          (term != null &&
+              termIds.any(
+                (id) =>
+                    id != term.id.toString() ||
+                    term.school != SupportedSchool.uestcGraduate,
+              ))) {
         throw const FormatException('文件中包含不同学期的课程');
       }
+      final undergraduateIds = courses
+          .map(
+            (c) =>
+                RegExp(r'^uestc-undergraduate-(\d+)-')
+                    .firstMatch(c.id)
+                    ?.group(1),
+          )
+          .whereType<String>()
+          .toSet();
+      if (undergraduateIds.isNotEmpty &&
+              (term?.school != SupportedSchool.uestcUndergraduate ||
+                  undergraduateIds.any((id) => id != term!.id.toString())) ||
+          courses.any((c) => c.endPeriod > 11) &&
+              (source == CourseSource.demo ||
+                  term?.school != SupportedSchool.uestcUndergraduate)) {
+        throw const FormatException('本科课表来源或学期无效');
+      }
       return ImportDraft(
         courses: List.unmodifiable(courses),
         explicitlyEmpty: json['explicitlyEmpty'] == true,