fix: harden school imports and add optional feedback diagnostics

mobile/lib/features/feedback/feedback_http_sender.dart

@@ -192,6 +192,14 @@ class HttpFeedbackSender implements FeedbackSender {
       bytes.add(attachment.bytes);
       write('\r\n');
     }
+    if (submission.diagnosticLog != null) {
+      write(
+        '--$boundary\r\nContent-Disposition: form-data; name="diagnostics"; filename="TPSchedule-diagnostics.txt"\r\n'
+        'Content-Type: text/plain; charset=utf-8\r\n\r\n',
+      );
+      bytes.add(submission.diagnosticLog!);
+      write('\r\n');
+    }
     write('--$boundary--\r\n');
     return bytes.takeBytes();
   }

mobile/lib/features/feedback/feedback_page.dart

@@ -2,6 +2,7 @@ import 'package:file_picker/file_picker.dart';
 import 'package:flutter/material.dart';
 
 import '../../app/app_theme.dart';
+import '../../services/diagnostic_log.dart';
 import 'feedback_submission.dart';
 
 typedef FeedbackAttachmentPicker = Future<FeedbackAttachment?> Function();
@@ -32,6 +33,7 @@ class _FeedbackPageState extends State<FeedbackPage> {
   var _picking = false;
   var _success = false;
   var _uncertain = false;
+  var _includeLogs = false;
   String? _error;
   FeedbackSubmission? _pendingSubmission;
 
@@ -103,6 +105,7 @@ class _FeedbackPageState extends State<FeedbackPage> {
     if (_submitting || _picking) return;
     if (!_uncertain && !(_form.currentState?.validate() ?? false)) return;
     FocusScope.of(context).unfocus();
+    setState(() => _submitting = true);
     try {
       _pendingSubmission ??= _kind == FeedbackKind.problem
           ? FeedbackSubmission.problem(
@@ -111,6 +114,9 @@ class _FeedbackPageState extends State<FeedbackPage> {
               contact: _contact.text,
               attachments: _attachments,
               limits: widget.limits,
+              diagnosticLog: _includeLogs
+                  ? await DiagnosticLog.instance.export()
+                  : null,
             )
           : FeedbackSubmission.development(
               id: FeedbackSubmission.newId(),
@@ -256,6 +262,24 @@ class _FeedbackPageState extends State<FeedbackPage> {
                               : null,
                         ),
                         if (_kind == FeedbackKind.problem) ...[
+                          CheckboxListTile(
+                            key: const Key('feedback-logs'),
+                            contentPadding: EdgeInsets.zero,
+                            title: const Text('附带近10分钟诊断日志'),
+                            subtitle: const Text(
+                              '包含登录跳转、课表读取及错误状态，帮助排查问题；不包含密码、验证码或课表内容。',
+                            ),
+                            value: _includeLogs,
+                            onChanged: _submitting
+                                ? null
+                                : (value) {
+                                    setState(() {
+                                      _includeLogs = value ?? false;
+                                      _pendingSubmission = null;
+                                      _error = null;
+                                    });
+                                  },
+                          ),
                           const SizedBox(height: 10),
                           const Text(
                             '图片或视频（选填）',

mobile/lib/features/feedback/feedback_submission.dart

@@ -102,6 +102,7 @@ class FeedbackSubmission {
     this.contact,
     this.school,
     this.attachments = const [],
+    this.diagnosticLog,
   });
 
   factory FeedbackSubmission.problem({
@@ -110,18 +111,26 @@ class FeedbackSubmission {
     String? contact,
     List<FeedbackAttachment> attachments = const [],
     FeedbackLimits limits = FeedbackLimits.defaults,
+    Uint8List? diagnosticLog,
   }) {
     final text = message.trim();
     if (text.isEmpty) throw const FeedbackException('请填写问题或建议');
     if (text.length > 5000) throw const FeedbackException('问题或建议不能超过 5000 个字符');
     _validateContact(contact);
     validateAttachments(attachments, limits);
+    if (diagnosticLog != null &&
+        (diagnosticLog.isEmpty || diagnosticLog.length > 256 * 1024)) {
+      throw const FeedbackException('日志附件不能超过256 KB');
+    }
     return FeedbackSubmission._(
       id: id,
       kind: FeedbackKind.problem,
       message: text,
       contact: _optional(contact),
       attachments: List.unmodifiable(attachments),
+      diagnosticLog: diagnosticLog == null
+          ? null
+          : Uint8List.fromList(diagnosticLog).asUnmodifiableView(),
     );
   }
 
@@ -151,6 +160,7 @@ class FeedbackSubmission {
   final String? contact;
   final String? school;
   final List<FeedbackAttachment> attachments;
+  final Uint8List? diagnosticLog;
 
   static String newId() {
     final random = Random.secure();