Add VoiceFAB component for voice call initiation

Floating action button that triggers voice calls with Julia AI.
Features:
- Animated show/hide based on active call state
- Press animation feedback
- Positioned above tab bar with safe area support
- Disabled state styling

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

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

components/VoiceFAB.tsx

@@ -0,0 +1,144 @@
+/**
+ * Voice Floating Action Button Component
+ *
+ * A floating action button for initiating voice calls with Julia AI.
+ * Shows on screens where voice chat is available.
+ * Hidden when a call is already active.
+ */
+
+import React, { useRef, useEffect } from 'react';
+import {
+  StyleSheet,
+  TouchableOpacity,
+  Animated,
+  ViewStyle,
+} from 'react-native';
+import { Ionicons } from '@expo/vector-icons';
+import { useSafeAreaInsets } from 'react-native-safe-area-context';
+import { AppColors, BorderRadius } from '@/constants/theme';
+import { useVoiceCall } from '@/contexts/VoiceCallContext';
+
+interface VoiceFABProps {
+  onPress: () => void;
+  style?: ViewStyle;
+  disabled?: boolean;
+}
+
+const FAB_SIZE = 56;
+
+export function VoiceFAB({ onPress, style, disabled = false }: VoiceFABProps) {
+  const { isCallActive } = useVoiceCall();
+  const insets = useSafeAreaInsets();
+
+  // Animation values
+  const scale = useRef(new Animated.Value(1)).current;
+  const opacity = useRef(new Animated.Value(1)).current;
+
+  // Hide FAB when call is active
+  useEffect(() => {
+    if (isCallActive) {
+      Animated.parallel([
+        Animated.timing(scale, {
+          toValue: 0,
+          duration: 200,
+          useNativeDriver: true,
+        }),
+        Animated.timing(opacity, {
+          toValue: 0,
+          duration: 200,
+          useNativeDriver: true,
+        }),
+      ]).start();
+    } else {
+      Animated.parallel([
+        Animated.spring(scale, {
+          toValue: 1,
+          friction: 5,
+          tension: 40,
+          useNativeDriver: true,
+        }),
+        Animated.timing(opacity, {
+          toValue: 1,
+          duration: 200,
+          useNativeDriver: true,
+        }),
+      ]).start();
+    }
+  }, [isCallActive, scale, opacity]);
+
+  // Press animation
+  const handlePressIn = () => {
+    Animated.spring(scale, {
+      toValue: 0.9,
+      friction: 5,
+      useNativeDriver: true,
+    }).start();
+  };
+
+  const handlePressOut = () => {
+    Animated.spring(scale, {
+      toValue: 1,
+      friction: 5,
+      useNativeDriver: true,
+    }).start();
+  };
+
+  // Don't render if call is active
+  if (isCallActive) {
+    return null;
+  }
+
+  return (
+    <Animated.View
+      style={[
+        styles.container,
+        {
+          bottom: insets.bottom + 80, // Above tab bar
+          transform: [{ scale }],
+          opacity,
+        },
+        style,
+      ]}
+    >
+      <TouchableOpacity
+        style={[styles.fab, disabled && styles.fabDisabled]}
+        onPress={onPress}
+        onPressIn={handlePressIn}
+        onPressOut={handlePressOut}
+        disabled={disabled}
+        activeOpacity={0.9}
+      >
+        <Ionicons
+          name="mic"
+          size={28}
+          color={disabled ? AppColors.textMuted : AppColors.white}
+        />
+      </TouchableOpacity>
+    </Animated.View>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    position: 'absolute',
+    right: 16,
+    zIndex: 100,
+  },
+  fab: {
+    width: FAB_SIZE,
+    height: FAB_SIZE,
+    borderRadius: BorderRadius.full,
+    backgroundColor: AppColors.success,
+    justifyContent: 'center',
+    alignItems: 'center',
+    shadowColor: '#000',
+    shadowOffset: { width: 0, height: 4 },
+    shadowOpacity: 0.3,
+    shadowRadius: 8,
+    elevation: 8,
+  },
+  fabDisabled: {
+    backgroundColor: AppColors.surface,
+    shadowOpacity: 0.1,
+  },
+});