feat: add AI voice transcription fallback for domestic Android ROMs

kouyu_english/lib/features/assessment/assessment_page.dart

@@ -1,3 +1,4 @@
+import '../../core/ai_service.dart';
 import 'package:flutter/material.dart';
 
 import '../../core/app_state.dart';
@@ -32,10 +33,11 @@ class _AssessmentPreparationPageState extends State<AssessmentPreparationPage> {
 
   Future<void> _checkMicrophone() async {
     setState(() => checkingMicrophone = true);
-    final ready = await VoiceService.instance.initializeSpeech();
+    final sttReady = await VoiceService.instance.initializeSpeech();
+    final recReady = await VoiceService.instance.hasRecordPermission();
     if (!mounted) return;
     setState(() {
-      microphoneReady = ready;
+      microphoneReady = sttReady || recReady;
       checkingMicrophone = false;
     });
   }
@@ -135,6 +137,8 @@ class _AssessmentPageState extends State<AssessmentPage> {
   bool transcriptEdited = false;
   String lastTranscript = '';
   bool listening = false;
+  bool transcribing = false;
+  bool aiVoiceRecording = false;
   bool audioPlayed = false;
   bool speakingUnavailable = false;
   AssessmentRecord? completedRecord;
@@ -166,31 +170,98 @@ class _AssessmentPageState extends State<AssessmentPage> {
   }
 
   Future<void> _mic() async {
+    if (aiVoiceRecording) {
+      final path = await VoiceService.instance.stopRecording();
+      if (!mounted) return;
+      setState(() {
+        aiVoiceRecording = false;
+        listening = false;
+        transcribing = true;
+      });
+      if (path != null) {
+        final config = widget.state.aiConfig;
+        final transcribed = await AiService.instance.transcribeAudio(
+          filePath: path,
+          provider: config.provider,
+          endpoint: config.endpoint,
+          model: config.model,
+        );
+        if (mounted) {
+          setState(() {
+            transcribing = false;
+            if (transcribed != null && transcribed.trim().isNotEmpty) {
+              controller.text = transcribed.trim();
+              usedMic = true;
+              lastTranscript = transcribed.trim();
+              transcriptEdited = false;
+              speakingUnavailable = false;
+            }
+          });
+          if (transcribed == null || transcribed.trim().isEmpty) {
+            ScaffoldMessenger.of(context).showSnackBar(
+              const SnackBar(content: Text('未识别到清晰语音，请再试一次。')),
+            );
+          }
+        }
+      } else {
+        if (mounted) setState(() => transcribing = false);
+      }
+      return;
+    }
+
     if (listening) {
       await VoiceService.instance.stopListening();
       if (mounted) setState(() => listening = false);
       return;
     }
-    final ready = await VoiceService.instance.startListening((text, _) {
+    final ready = await VoiceService.instance.startListening(
+      (text, _) {
+        if (mounted) {
+          setState(() {
+            controller.text = text;
+            usedMic = true;
+            lastTranscript = text;
+            transcriptEdited = false;
+          });
+        }
+      },
+      onStatus: (status) {
+        if (mounted && (status == 'notListening' || status == 'done')) {
+          setState(() => listening = false);
+        }
+      },
+      onError: (err) {
+        if (mounted) {
+          setState(() => listening = false);
+        }
+      },
+    );
+    if (!ready) {
+      final recordStarted = await VoiceService.instance.startRecording();
       if (mounted) {
         setState(() {
-          controller.text = text;
-          usedMic = true;
-          lastTranscript = text;
+          aiVoiceRecording = recordStarted;
+          listening = recordStarted;
+          speakingUnavailable = !recordStarted;
         });
+        if (recordStarted) {
+          ScaffoldMessenger.of(context).showSnackBar(
+            const SnackBar(content: Text('已启动麦克风录音，回答后再次点击，AI 将自动转写为英文。')),
+          );
+        } else {
+          ScaffoldMessenger.of(context).showSnackBar(
+            const SnackBar(content: Text('无法访问麦克风，口语可稍后补测。')),
+          );
+        }
       }
-    });
+      return;
+    }
     if (mounted) {
       setState(() {
         listening = ready;
         speakingUnavailable = !ready;
       });
     }
-    if (!ready && mounted) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        const SnackBar(content: Text('语音识别不可用；口语可稍后补测，不会判为语言错误。')),
-      );
-    }
   }
 
   bool _openCorrect() {
@@ -409,8 +480,10 @@ class _AssessmentPageState extends State<AssessmentPage> {
             ),
             if (task.skill == AssessmentSkill.speaking)
               SecondaryButton(
-                label: listening ? '停止录音' : '使用麦克风回答',
-                onPressed: _mic,
+                label: transcribing
+                    ? '正在 AI 识别…'
+                    : (listening ? '停止录音并识别' : '使用麦克风回答'),
+                onPressed: transcribing ? null : _mic,
               ),
             if (task.skill == AssessmentSkill.speaking && speakingUnavailable)
               SecondaryButton(