Add toggle listening mode on VoiceFAB tap

- FAB now toggles between idle and listening states
- Green background (idle) → Red background (listening)
- Icon switches between mic-outline and mic
- Connects to VoiceContext for state management

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/(tabs)/_layout.tsx

@@ -1,6 +1,6 @@
 import { Tabs } from 'expo-router';
 import React, { useCallback } from 'react';
-import { Platform, View, Alert } from 'react-native';
+import { Platform, View } from 'react-native';
 import { Feather } from '@expo/vector-icons';
 import { useSafeAreaInsets } from 'react-native-safe-area-context';
 
@@ -9,6 +9,7 @@ import { VoiceFAB } from '@/components/VoiceFAB';
 import { AppColors } from '@/constants/theme';
 import { useColorScheme } from '@/hooks/use-color-scheme';
 import { useVoiceCall } from '@/contexts/VoiceCallContext';
+import { useVoice } from '@/contexts/VoiceContext';
 
 export default function TabLayout() {
   const colorScheme = useColorScheme();
@@ -17,15 +18,17 @@ export default function TabLayout() {
   // VoiceFAB uses VoiceCallContext internally to hide when call is active
   useVoiceCall(); // Ensure context is available
 
-  // Handle voice FAB press - initiate voice call
+  // Voice context for listening mode toggle
+  const { isListening, startSession, stopSession } = useVoice();
+
+  // Handle voice FAB press - toggle listening mode
   const handleVoiceFABPress = useCallback(() => {
-    // TODO: Integrate with voice call service when ready
-    Alert.alert(
-      'Voice Call',
-      'Voice call with Julia AI will be available soon.',
-      [{ text: 'OK' }]
-    );
-  }, []);
+    if (isListening) {
+      stopSession();
+    } else {
+      startSession();
+    }
+  }, [isListening, startSession, stopSession]);
 
   // Calculate tab bar height based on safe area
   // On iOS with home indicator, insets.bottom is ~34px
@@ -116,8 +119,8 @@ export default function TabLayout() {
         />
       </Tabs>
 
-      {/* Voice FAB - shown when no call is active */}
-      <VoiceFAB onPress={handleVoiceFABPress} />
+      {/* Voice FAB - toggle listening mode */}
+      <VoiceFAB onPress={handleVoiceFABPress} isListening={isListening} />
     </View>
   );
 }

components/VoiceFAB.tsx

@@ -1,8 +1,8 @@
 /**
  * Voice Floating Action Button Component
  *
- * A floating action button for initiating voice calls with Julia AI.
- * Shows on screens where voice chat is available.
+ * A floating action button for toggling voice listening mode.
+ * Tap to start/stop listening.
  * Hidden when a call is already active.
  */
 
@@ -23,11 +23,12 @@ interface VoiceFABProps {
   onPress: () => void;
   style?: ViewStyle;
   disabled?: boolean;
+  isListening?: boolean;
 }
 
 const FAB_SIZE = 56;
 
-export function VoiceFAB({ onPress, style, disabled = false }: VoiceFABProps) {
+export function VoiceFAB({ onPress, style, disabled = false, isListening = false }: VoiceFABProps) {
   const { isCallActive } = useVoiceCall();
   const insets = useSafeAreaInsets();
 
@@ -103,7 +104,11 @@ export function VoiceFAB({ onPress, style, disabled = false }: VoiceFABProps) {
       ]}
     >
       <TouchableOpacity
-        style={[styles.fab, disabled && styles.fabDisabled]}
+        style={[
+          styles.fab,
+          isListening && styles.fabListening,
+          disabled && styles.fabDisabled,
+        ]}
         onPress={onPress}
         onPressIn={handlePressIn}
         onPressOut={handlePressOut}
@@ -111,7 +116,7 @@ export function VoiceFAB({ onPress, style, disabled = false }: VoiceFABProps) {
         activeOpacity={0.9}
       >
         <Ionicons
-          name="mic"
+          name={isListening ? 'mic' : 'mic-outline'}
           size={28}
           color={disabled ? AppColors.textMuted : AppColors.white}
         />
@@ -141,6 +146,9 @@ const styles = StyleSheet.create({
     shadowRadius: 8,
     elevation: 8,
   },
+  fabListening: {
+    backgroundColor: AppColors.error,
+  },
   fabDisabled: {
     backgroundColor: AppColors.surface,
     shadowOpacity: 0.1,