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/lesson/lesson_flow.dart

@@ -101,7 +101,7 @@ class _LessonFlowState extends State<LessonFlow> {
             state: widget.state,
             initialText: activity.listening,
           ),
-          onContinue: listeningAudioPlayed && selectedAnswer == 0
+          onContinue: selectedAnswer == 0
               ? widget.state.completeListening
               : null,
         );
@@ -192,6 +192,7 @@ class _LessonFlowState extends State<LessonFlow> {
     return _LessonScope(
       title:
           '第 ${lesson.number} 课 · ${lesson.title} · 第 ${widget.state.activeSegmentIndexFor(lesson.id) + 1}/${lesson.segments.length} 段',
+      onExit: widget.onFinish,
       child: content,
     );
   }
@@ -205,7 +206,21 @@ class _LessonScaffold extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) => AppPage(
-    appBar: AppBar(title: Text(_LessonScope.of(context))),
+    appBar: AppBar(
+      leading: IconButton(
+        icon: const Icon(Icons.arrow_back),
+        tooltip: "退出课程",
+        onPressed: () {
+          final onExit = _LessonScope.exitOf(context);
+          if (onExit != null) {
+            onExit();
+          } else if (Navigator.canPop(context)) {
+            Navigator.pop(context);
+          }
+        },
+      ),
+      title: Text(_LessonScope.of(context)),
+    ),
     child: SpacedColumn(
       spacing: 16,
       children: [
@@ -231,16 +246,25 @@ class _LessonScaffold extends StatelessWidget {
 }
 
 class _LessonScope extends InheritedWidget {
-  const _LessonScope({required this.title, required super.child});
+  const _LessonScope({
+    required this.title,
+    this.onExit,
+    required super.child,
+  });
 
   final String title;
+  final VoidCallback? onExit;
 
   static String of(BuildContext context) =>
       context.dependOnInheritedWidgetOfExactType<_LessonScope>()?.title ??
       'A0 课程练习';
 
+  static VoidCallback? exitOf(BuildContext context) =>
+      context.dependOnInheritedWidgetOfExactType<_LessonScope>()?.onExit;
+
   @override
-  bool updateShouldNotify(_LessonScope oldWidget) => title != oldWidget.title;
+  bool updateShouldNotify(_LessonScope oldWidget) =>
+      title != oldWidget.title || onExit != oldWidget.onExit;
 }
 
 class _PreviewStep extends StatelessWidget {
@@ -357,7 +381,12 @@ class _ListeningStep extends StatelessWidget {
           for (var index = 0; index < answers.length; index++)
             SectionCard(
               tint: selectedAnswer == index ? AppColors.softGreen : null,
-              onTap: audioPlayed ? () => onSelected(index) : null,
+              onTap: () {
+                onSelected(index);
+                if (!audioPlayed) {
+                  onPlayed();
+                }
+              },
               child: Row(
                 children: [
                   Icon(
@@ -374,7 +403,9 @@ class _ListeningStep extends StatelessWidget {
               ),
             ),
           PrimaryButton(
-            label: audioPlayed ? '检查并继续' : '先播放音频',
+            label: selectedAnswer >= 0
+                ? '检查并继续'
+                : (audioPlayed ? '请选择答案' : '先播放音频或选择答案'),
             onPressed: onContinue,
           ),
           if (selectedAnswer >= 0 && selectedAnswer != 0)
@@ -1126,16 +1157,38 @@ class _AudioRow extends StatelessWidget {
     children: [
       IconButton.filled(
         onPressed: () async {
-          await VoiceService.instance.speak(speech ?? label);
-          onPlayed?.call();
+          try {
+            await VoiceService.instance.speak(speech ?? label);
+          } finally {
+            onPlayed?.call();
+          }
         },
         icon: const Icon(Icons.play_arrow),
       ),
       const SizedBox(width: 10),
-      Expanded(child: Text(label)),
+      Expanded(
+        child: InkWell(
+          onTap: () async {
+            try {
+              await VoiceService.instance.speak(speech ?? label);
+            } finally {
+              onPlayed?.call();
+            }
+          },
+          child: Padding(
+            padding: const EdgeInsets.symmetric(vertical: 8.0),
+            child: Text(label),
+          ),
+        ),
+      ),
       TextButton(
-        onPressed: () =>
-            VoiceService.instance.speak(speech ?? label, slow: true),
+        onPressed: () async {
+          try {
+            await VoiceService.instance.speak(speech ?? label, slow: true);
+          } finally {
+            onPlayed?.call();
+          }
+        },
         child: const Text('慢速'),
       ),
     ],