feat: model undergraduate schools terms and exam queries

mobile/lib/domain/course.dart

@@ -11,12 +11,14 @@ class Course {
     required this.endPeriod,
     required Set<int> weeks,
     required this.source,
+    this.courseCode = '',
+    this.notes = '',
   }) : weeks = Set.unmodifiable(weeks) {
     if ([id, name, teacher, room].any((value) => value.trim().isEmpty) ||
         weekday < 1 ||
         weekday > 7 ||
         startPeriod < 1 ||
-        endPeriod > 11 ||
+        endPeriod > 12 ||
         endPeriod < startPeriod ||
         weeks.isEmpty ||
         weeks.any((week) => week < 1 || week > 30)) {
@@ -24,6 +26,7 @@ class Course {
     }
   }
   final String id, name, teacher, room;
+  final String courseCode, notes;
   final int weekday, startPeriod, endPeriod;
   final Set<int> weeks;
   final CourseSource source;
@@ -38,6 +41,8 @@ class Course {
     'endPeriod': endPeriod,
     'weeks': weeks.toList()..sort(),
     'source': source.name,
+    'courseCode': courseCode,
+    'notes': notes,
   };
 
   static Course fromJson(Map<String, dynamic> json, {CourseSource? source}) {
@@ -62,6 +67,8 @@ class Course {
         endPeriod: json['endPeriod'] as int,
         weeks: rawWeeks.cast<int>().toSet(),
         source: source ?? CourseSource.values.byName(json['source'] as String),
+        courseCode: (json['courseCode'] ?? '') as String,
+        notes: (json['notes'] ?? '') as String,
       );
     } catch (_) {
       throw const FormatException('课程字段、节次或周次无效');