fix: harden school imports and add optional feedback diagnostics

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）',