fix: import unpublished exam rooms and add opt-in school HTML feedback

mobile/lib/features/school/undergraduate/activity_data.dart

@@ -1,3 +1,13 @@
+class UndergraduateActivityException extends FormatException {
+  const UndergraduateActivityException(
+    this.code,
+    String message,
+    this.activityNumber,
+  ) : super(message);
+  final String code;
+  final int activityNumber;
+}
+
 class UndergraduateActivity {
   UndergraduateActivity(
     this.teacher,
@@ -30,8 +40,26 @@ List<UndergraduateActivity> parseActivityData(
     final m = matches[i], args = _strings(m[1]!);
     if (args.length != 7) throw const FormatException('课程活动字段不完整');
     final suffix = RegExp(r'\(([A-Za-z0-9_.-]+)\)$').firstMatch(args[3]);
-    if (suffix == null || args[1].trim().isEmpty || args[5].trim().isEmpty) {
-      throw const FormatException('教师、教室或课程序号缺失');
+    if (suffix == null) {
+      throw UndergraduateActivityException(
+        'course_sequence_invalid',
+        '课程序号格式无法识别，请附带网页反馈',
+        i + 1,
+      );
+    }
+    if (args[1].trim().isEmpty) {
+      throw UndergraduateActivityException(
+        'teacher_missing',
+        '课程活动未提供教师信息，请附带网页反馈',
+        i + 1,
+      );
+    }
+    if (args[5].trim().isEmpty) {
+      throw UndergraduateActivityException(
+        'room_missing',
+        '课程活动未提供教室信息，请附带网页反馈',
+        i + 1,
+      );
     }
     final bitmap = args[6];
     if (!RegExp(r'^0[01]+$').hasMatch(bitmap) ||