Fix Android voice bugs - STT restart and token retry

Critical Android fixes:

BUG 1 - STT not restarting after TTS:
- Problem: isSpeaking delay (300ms iOS visual) blocked Android STT
- Android audio focus conflict: STT cannot start while isSpeaking=true
- Fix: Platform-specific isSpeaking timing
  - iOS: 300ms delay (smooth visual indicator)
  - Android: immediate (allows STT to restart)

BUG 2 - Session expired loop:
- Problem: 401 error → token reset → no retry → user hears error
- Fix: Automatic token refresh and retry on 401
- Flow: 401 → clear token → get new token → retry request
- User never hears "Session expired" unless retry also fails

contexts/VoiceContext.tsx:12-23,387-360

contexts/VoiceContext.tsx

@@ -17,6 +17,7 @@ import React, {
   useRef,
   ReactNode,
 } from 'react';
+import { Platform } from 'react-native';
 import * as Speech from 'expo-speech';
 import { api } from '@/services/api';
 import { useVoiceTranscript } from './VoiceTranscriptContext';
@@ -322,10 +323,42 @@ export function VoiceProvider({ children }: { children: ReactNode }) {
 
           return responseText;
         } else {
-          // Token might be expired
+          // Token might be expired - retry with new token
           if (data.status === '401 Unauthorized') {
+            console.log('[VoiceContext] Token expired, retrying with new token...');
             apiTokenRef.current = null;
-            throw new Error('Session expired, please try again');
+
+            // Get new token and retry request
+            const newToken = await getWellNuoToken();
+
+            const retryRequestParams: Record<string, string> = {
+              function: voiceApiType,
+              clientId: 'MA_001',
+              user_name: WELLNUO_USER,
+              token: newToken,
+              question: normalizedQuestion,
+              deployment_id: deploymentId,
+            };
+
+            const retryResponse = await fetch(API_URL, {
+              method: 'POST',
+              headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
+              body: new URLSearchParams(retryRequestParams).toString(),
+              signal: abortController.signal,
+            });
+
+            const retryData = await retryResponse.json();
+
+            if (retryData.ok && retryData.response?.body) {
+              const responseText = retryData.response.body;
+              console.log('[VoiceContext] Retry succeeded:', responseText.slice(0, 100) + '...');
+              setLastResponse(responseText);
+              addTranscriptEntry('assistant', responseText);
+              await speak(responseText);
+              return responseText;
+            } else {
+              throw new Error(retryData.message || 'Could not get response after retry');
+            }
           }
           throw new Error(data.message || 'Could not get response');
         }
@@ -400,11 +433,15 @@ export function VoiceProvider({ children }: { children: ReactNode }) {
         },
         onDone: () => {
           console.log('[VoiceContext] TTS completed');
-          // Delay turning off green indicator to match STT restart delay (300ms)
-          // This keeps the visual indicator on during the transition period
+          // On iOS: Delay turning off green indicator to match STT restart delay (300ms)
+          // On Android: Turn off immediately (audio focus conflict with STT)
+          if (Platform.OS === 'ios') {
             setTimeout(() => {
               setIsSpeaking(false);
             }, 300);
+          } else {
+            setIsSpeaking(false);
+          }
           // Return to listening state after speaking (if session wasn't stopped)
           if (!sessionStoppedRef.current) {
             setStatus('listening');