feat: integrate undergraduate school workflows and period twelve

mobile/lib/domain/app_snapshot.dart

@@ -43,6 +43,26 @@ class AppSnapshot {
   final Map<String, String> calendarEventIds;
   final bool calendarCleanupPending;
   final SupportedSchool? selectedSchool;
+  static void validateCourseSource(List<Course> courses, SchoolTerm? term) {
+    if (term?.school != SupportedSchool.uestcUndergraduate &&
+        courses.any((c) => c.endPeriod > 11)) {
+      throw const FormatException('第12节需要本科课表来源');
+    }
+    for (final course in courses) {
+      final under = RegExp(r'^uestc-undergraduate-(\d+)-')
+          .firstMatch(course.id);
+      if (under != null &&
+          (term?.school != SupportedSchool.uestcUndergraduate ||
+              under[1] != term?.id.toString())) {
+        throw const FormatException('本科课程学校或学期不一致');
+      }
+      if (term?.school == SupportedSchool.uestcUndergraduate &&
+          RegExp(r'^uestc-\d+-').hasMatch(course.id)) {
+        throw const FormatException('本科课表包含研究生课程标识');
+      }
+    }
+  }
+
   static SchoolTerm? _legacyTerm(List<Course> courses, ExamSchedule? exams) {
     final ids = courses
         .map(
@@ -195,9 +215,7 @@ class AppSnapshot {
           (k, v) => MapEntry(k as String, v as String),
         ),
       );
-      if (snapshot.schoolTerm?.school != SupportedSchool.uestcUndergraduate &&
-          values.any((c) => c.endPeriod > 11))
-        throw const FormatException('第12节需要本科课表来源');
+      validateCourseSource(values, snapshot.schoolTerm);
       return snapshot;
     } catch (_) {
       throw const FormatException('保存文件内容无效，未覆盖已有数据');

mobile/lib/domain/lesson_times.dart

@@ -15,6 +15,7 @@ const lessonSlots = [
   LessonSlot(9, 1170, 1215),
   LessonSlot(10, 1220, 1265),
   LessonSlot(11, 1270, 1315),
+  LessonSlot(12, 1320, 1365),
 ];
 String minuteLabel(int minute) =>
     '${(minute ~/ 60).toString().padLeft(2, '0')}:${(minute % 60).toString().padLeft(2, '0')}';