feat(mobile): track mobile app scaffold

mobile/app/src/platform/voice/voiceInput.ts

@@ -0,0 +1,25 @@
+import { useAudioRecorder, RecordingPresets } from 'expo-audio';
+
+export function useVoiceRecorder() {
+  const recorder = useAudioRecorder(RecordingPresets.HIGH_QUALITY);
+
+  return {
+    recorder,
+    async start() {
+      await recorder.prepareToRecordAsync();
+      recorder.record();
+    },
+    async stop() {
+      await recorder.stop();
+      return recorder.uri;
+    },
+  };
+}
+
+export async function transcribeVoice(uri: string) {
+  // 后续接入 /api/v1/mobile/voice/transcribe；初始化阶段先返回可见占位结果。
+  return {
+    text: `已收到语音文件：${uri.split('/').pop() || 'voice-recording'}`,
+    confidence: 0,
+  };
+}