fix: 优化语音识别功能，增加转写中状态和错误处理

apps/lib/features/home/ui/screens/home_screen.dart

@@ -29,6 +29,8 @@ const _inputRadius = 24.0;
 const _scrollDurationMs = 300;
 const _rippleDurationMs = 1200;
 const _recordingDotSize = 10.0;
+const _transcribingSpinnerSize = 18.0;
+const _transcribingStrokeWidth = 2.0;
 
 /// 颜色常量
 const _chatBgColor = Color(0xFFF8FAFC);
@@ -446,6 +448,8 @@ class _HomeScreenState extends State<HomeScreen>
                   Expanded(
                     child: _isRecording
                         ? _buildListeningIndicator()
+                        : _isTranscribing
+                        ? _buildTranscribingIndicator()
                         : TextField(
                             controller: _messageController,
                             minLines: 1,
@@ -474,15 +478,24 @@ class _HomeScreenState extends State<HomeScreen>
                         : _hasMessage
                         ? () => _sendMessage(context)
                         : _startRecording,
-                    child: Icon(
-                      _isRecording || _hasMessage
-                          ? LucideIcons.send
-                          : LucideIcons.mic,
-                      size: _iconSize,
-                      color: _isRecording || _hasMessage
-                          ? AppColors.blue600
-                          : AppColors.slate500,
-                    ),
+                    child: _isTranscribing
+                        ? const SizedBox(
+                            width: _transcribingSpinnerSize,
+                            height: _transcribingSpinnerSize,
+                            child: CircularProgressIndicator(
+                              strokeWidth: _transcribingStrokeWidth,
+                              color: AppColors.blue600,
+                            ),
+                          )
+                        : Icon(
+                            _isRecording || _hasMessage
+                                ? LucideIcons.send
+                                : LucideIcons.mic,
+                            size: _iconSize,
+                            color: _isRecording || _hasMessage
+                                ? AppColors.blue600
+                                : AppColors.slate500,
+                          ),
                   ),
                 ],
               ),
@@ -496,6 +509,7 @@ class _HomeScreenState extends State<HomeScreen>
   Future<void> _sendMessage(BuildContext context) async {
     final content = _messageController.text.trim();
     if (content.isEmpty) return;
+    FocusScope.of(context).unfocus();
     _messageController.clear();
     context.read<ChatBloc>().sendMessage(content);
 
@@ -548,6 +562,27 @@ class _HomeScreenState extends State<HomeScreen>
     );
   }
 
+  Widget _buildTranscribingIndicator() {
+    return TweenAnimationBuilder<double>(
+      tween: Tween<double>(begin: 0.0, end: 1.0),
+      duration: const Duration(milliseconds: 180),
+      builder: (context, value, child) {
+        return Opacity(opacity: value, child: child);
+      },
+      child: const SizedBox(
+        key: ValueKey('transcribing_indicator'),
+        height: _inputMinHeight,
+        child: Align(
+          alignment: Alignment.centerLeft,
+          child: Text(
+            '语音识别中...',
+            style: TextStyle(fontSize: 14, color: AppColors.slate500),
+          ),
+        ),
+      ),
+    );
+  }
+
   Widget _buildWaveDot({required double scale}) {
     return Transform.scale(
       scale: scale,
@@ -599,13 +634,18 @@ class _HomeScreenState extends State<HomeScreen>
       if (!mounted) {
         return;
       }
+      final normalizedTranscript = transcript.trim();
+      if (normalizedTranscript.isEmpty) {
+        Toast.show(context, '未识别到有效语音，请靠近麦克风并连续说话后重试', type: ToastType.error);
+        return;
+      }
       _messageController.text = transcript;
       _messageController.selection = TextSelection.fromPosition(
         TextPosition(offset: transcript.length),
       );
-      if (autoSendAfterTranscribe && transcript.trim().isNotEmpty) {
+      if (autoSendAfterTranscribe) {
         _messageController.clear();
-        await _autoSendTranscript(transcript.trim());
+        await _autoSendTranscript(normalizedTranscript);
       }
     } catch (error) {
       if (!mounted) {
@@ -613,11 +653,15 @@ class _HomeScreenState extends State<HomeScreen>
       }
       Toast.show(context, _readableError(error), type: ToastType.error);
     } finally {
-      if (audioPath != null) {
-        final file = File(audioPath);
-        if (await file.exists()) {
-          await file.delete();
+      try {
+        if (audioPath != null) {
+          final file = File(audioPath);
+          if (await file.exists()) {
+            await file.delete();
+          }
         }
+      } catch (_) {
+        // Ignore temp file cleanup errors to avoid blocking UI state recovery.
       }
       if (mounted) {
         setState(() {