feat: scaffold ShieldAI React Native mobile app MVP (FRE-4572)

Build complete Expo/React Native mobile app with:
- Auth flow: email/password login, registration, biometric auth
- Dashboard: exposure summary, spam stats, voice protection status
- DarkWatch: watch list management, exposure feed, alert toggles
- SpamShield: call/text history, whitelist/blacklist management
- VoicePrint: family member enrollment, voice analysis
- Settings: tier management, notification preferences, security
- Push notification integration via FCM/APNs
- Offline-first state management with Zustand + AsyncStorage
- Integration with @shieldai/mobile-api-client for API services
- React Navigation with auth-aware routing (stack + bottom tabs)
- Dark theme with consistent design system (colors, spacing, typography)
- Network status monitoring and offline request queuing

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/mobile/src/components/Loading.tsx

@@ -0,0 +1,73 @@
+import React from 'react';
+import { StyleSheet, View, ActivityIndicator, Text } from 'react-native';
+import { COLORS, SPACING } from '@/constants/theme';
+
+interface LoadingOverlayProps {
+  visible: boolean;
+}
+
+export function LoadingOverlay({ visible }: LoadingOverlayProps) {
+  if (!visible) return null;
+
+  return (
+    <View style={styles.overlay}>
+      <ActivityIndicator size="large" color={COLORS.primary} />
+    </View>
+  );
+}
+
+interface EmptyStateProps {
+  title: string;
+  message?: string;
+}
+
+export function EmptyState({ title, message }: EmptyStateProps) {
+  return (
+    <View style={styles.emptyContainer}>
+      <View style={styles.emptyContent}>
+        <View style={styles.emptyIcon} />
+        <View style={styles.emptyText}>
+          <Text style={styles.emptyTitle}>{title}</Text>
+          {message && <Text style={styles.emptyMessage}>{message}</Text>}
+        </View>
+      </View>
+    </View>
+  );
+}
+
+const styles = StyleSheet.create({
+  overlay: {
+    ...StyleSheet.absoluteFillObject,
+    backgroundColor: 'rgba(0, 0, 0, 0.3)',
+    justifyContent: 'center',
+    alignItems: 'center',
+  },
+  emptyContainer: {
+    flex: 1,
+    justifyContent: 'center',
+    alignItems: 'center',
+    padding: SPACING.xl,
+  },
+  emptyContent: {
+    alignItems: 'center',
+  },
+  emptyIcon: {
+    width: 48,
+    height: 48,
+    borderRadius: 24,
+    backgroundColor: COLORS.card,
+    marginBottom: SPACING.md,
+  },
+  emptyText: {
+    alignItems: 'center',
+  },
+  emptyTitle: {
+    color: COLORS.textSecondary,
+    fontSize: 16,
+    fontWeight: '600',
+  },
+  emptyMessage: {
+    color: COLORS.textMuted,
+    fontSize: 14,
+  },
+});