fix: import unpublished exam rooms and add opt-in school HTML feedback

mobile/lib/features/feedback/feedback_submission.dart

@@ -103,6 +103,7 @@ class FeedbackSubmission {
     this.school,
     this.attachments = const [],
     this.diagnosticLog,
+    this.diagnosticHtml,
   });
 
   factory FeedbackSubmission.problem({
@@ -112,6 +113,7 @@ class FeedbackSubmission {
     List<FeedbackAttachment> attachments = const [],
     FeedbackLimits limits = FeedbackLimits.defaults,
     Uint8List? diagnosticLog,
+    Uint8List? diagnosticHtml,
   }) {
     final text = message.trim();
     if (text.isEmpty) throw const FeedbackException('请填写问题或建议');
@@ -122,6 +124,10 @@ class FeedbackSubmission {
         (diagnosticLog.isEmpty || diagnosticLog.length > 256 * 1024)) {
       throw const FeedbackException('日志附件不能超过256 KB');
     }
+    if (diagnosticHtml != null &&
+        (diagnosticHtml.isEmpty || diagnosticHtml.length > 2 * 1024 * 1024)) {
+      throw const FeedbackException('网页排查附件不能超过2 MB');
+    }
     return FeedbackSubmission._(
       id: id,
       kind: FeedbackKind.problem,
@@ -131,6 +137,9 @@ class FeedbackSubmission {
       diagnosticLog: diagnosticLog == null
           ? null
           : Uint8List.fromList(diagnosticLog).asUnmodifiableView(),
+      diagnosticHtml: diagnosticHtml == null
+          ? null
+          : Uint8List.fromList(diagnosticHtml).asUnmodifiableView(),
     );
   }
 
@@ -161,6 +170,7 @@ class FeedbackSubmission {
   final String? school;
   final List<FeedbackAttachment> attachments;
   final Uint8List? diagnosticLog;
+  final Uint8List? diagnosticHtml;
 
   static String newId() {
     final random = Random.secure();