feat: 增加AI配置文件与TTS自动朗读，修复二级页面返回按钮与音频播放

kouyu_english/lib/features/assessment/assessment_page.dart

@@ -46,7 +46,14 @@ class _AssessmentPreparationPageState extends State<AssessmentPreparationPage> {
     final canResume = draft != null && draft.packId == widget.pack.id;
     final pack = widget.pack;
     return AppPage(
-      appBar: AppBar(title: const Text('评估准备')),
+      appBar: AppBar(
+        leading: IconButton(
+          icon: const Icon(Icons.arrow_back),
+          tooltip: "返回",
+          onPressed: widget.onBack,
+        ),
+        title: const Text('评估准备'),
+      ),
       child: SpacedColumn(
         children: [
           Eyebrow('A0 阶段评估 · ${pack.id}'),
@@ -152,7 +159,9 @@ class _AssessmentPageState extends State<AssessmentPage> {
   }
 
   Future<void> _play() async {
-    await VoiceService.instance.speak(task.audio!);
+    try {
+      await VoiceService.instance.speak(task.audio!);
+    } catch (_) {}
     if (mounted) setState(() => audioPlayed = true);
   }
 
@@ -285,6 +294,14 @@ class _AssessmentPageState extends State<AssessmentPage> {
     final record = completedRecord;
     if (record != null) {
       return AppPage(
+        appBar: AppBar(
+          leading: IconButton(
+            icon: const Icon(Icons.arrow_back),
+            tooltip: "返回",
+            onPressed: widget.onFinished,
+          ),
+          title: Text(record.passed ? "阶段评估通过" : "阶段评估结果"),
+        ),
         child: SpacedColumn(
           children: [
             const Eyebrow('评估结果已保存'),
@@ -325,6 +342,11 @@ class _AssessmentPageState extends State<AssessmentPage> {
     }
     return AppPage(
       appBar: AppBar(
+        leading: IconButton(
+          icon: const Icon(Icons.arrow_back),
+          tooltip: "退出评估",
+          onPressed: widget.onFinished,
+        ),
         title: Text(
           'A0 评估 ${widget.pack.id} · ${index + 1}/${widget.pack.tasks.length}',
         ),
@@ -344,7 +366,12 @@ class _AssessmentPageState extends State<AssessmentPage> {
             const Text('请根据听到的内容选择答案。'),
             for (var i = 0; i < task.choices.length; i++)
               SectionCard(
-                onTap: audioPlayed ? () => _submit(i) : null,
+                onTap: () {
+                  if (!audioPlayed) {
+                    _play();
+                  }
+                  _submit(i);
+                },
                 child: Text(task.choices[i]),
               ),
           ] else if (task.skill == AssessmentSkill.reading) ...[