feat: 完善听力口语辅助状态记录、练习分块与复习抽查间隔机制

kouyu_english/lib/core/voice_service.dart

@@ -77,7 +77,7 @@ class VoiceService {
     } catch (_) {}
   }
 
-  Future<void> speak(String text, {bool slow = false}) async {
+  Future<bool> speak(String text, {bool slow = false}) async {
     try {
       await stopRecordingPlayback();
       await _initTts();
@@ -95,8 +95,11 @@ class VoiceService {
         } catch (_) {}
       }
       await _tts.setSpeechRate(slow ? 0.35 : 0.48);
-      await _tts.speak(text);
-    } catch (_) {}
+      final result = await _tts.speak(text);
+      return result == 1 || result == true;
+    } catch (_) {
+      return false;
+    }
   }
 
   Future<void> stopSpeaking() async {