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/screens/auth/LoginScreen.tsx

@@ -0,0 +1,146 @@
+import React, { useState } from 'react';
+import { StyleSheet, Text, View, SafeAreaView, KeyboardAvoidingView, Platform, ScrollView, Alert } from 'react-native';
+import { RouteProp, useRoute, useNavigation } from '@react-navigation/native';
+import { useAuthStore } from '@/store/authStore';
+import { Button, Input } from '@/components';
+import { COLORS, FONT_SIZES, SPACING } from '@/constants/theme';
+
+type RootStackParamList = {
+  Login: undefined;
+  Register: undefined;
+  App: undefined;
+};
+
+type LoginScreenRouteProp = RouteProp<RootStackParamList, 'Login'>;
+
+export function LoginScreen() {
+  const route = useRoute<LoginScreenRouteProp>();
+  const navigation = useNavigation<any>();
+  const { login, isLoading, error, clearError } = useAuthStore();
+
+  const [email, setEmail] = useState('');
+  const [password, setPassword] = useState('');
+  const [formError, setFormError] = useState('');
+
+  const handleLogin = async () => {
+    setFormError('');
+    clearError();
+
+    if (!email || !password) {
+      setFormError('Please fill in all fields');
+      return;
+    }
+
+    try {
+      await login(email, password);
+    } catch (err: any) {
+      setFormError(err.message || 'Login failed. Please try again.');
+      Alert.alert('Login Failed', err.message || 'Please check your credentials and try again.');
+    }
+  };
+
+  return (
+    <SafeAreaView style={styles.container}>
+      <KeyboardAvoidingView
+        behavior={Platform.OS === 'ios' ? 'padding' : 'height'}
+        style={styles.keyboardView}
+      >
+        <ScrollView contentContainerStyle={styles.scrollContent}>
+          <View style={styles.header}>
+            <Text style={styles.logo}>ShieldAI</Text>
+            <Text style={styles.tagline}>Your digital protection suite</Text>
+          </View>
+
+          <View style={styles.form}>
+            {formError && <Text style={styles.error}>{formError}</Text>}
+
+            <Input
+              label="Email"
+              placeholder="you@example.com"
+              value={email}
+              onChangeText={setEmail}
+              autoCapitalize="none"
+              keyboardType="email-address"
+              autoComplete="email"
+            />
+
+            <Input
+              label="Password"
+              placeholder="••••••••"
+              value={password}
+              onChangeText={setPassword}
+              secureTextEntry
+              autoComplete="password"
+            />
+
+            <Button
+              title={isLoading ? 'Signing in...' : 'Sign In'}
+              onPress={handleLogin}
+              disabled={isLoading}
+              fullWidth
+            />
+
+            <View style={styles.footer}>
+              <Text style={styles.footerText}>Don't have an account? </Text>
+              <Text style={styles.link} onPress={() => navigation.navigate('Register')}>
+                Sign Up
+              </Text>
+            </View>
+          </View>
+        </ScrollView>
+      </KeyboardAvoidingView>
+    </SafeAreaView>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+    backgroundColor: COLORS.background,
+  },
+  keyboardView: {
+    flex: 1,
+  },
+  scrollContent: {
+    flexGrow: 1,
+    justifyContent: 'center',
+    padding: SPACING.lg,
+  },
+  header: {
+    alignItems: 'center',
+    marginBottom: SPACING.xxl,
+  },
+  logo: {
+    color: COLORS.primary,
+    fontSize: FONT_SIZES.xxxl,
+    fontWeight: 'bold',
+  },
+  tagline: {
+    color: COLORS.textSecondary,
+    fontSize: FONT_SIZES.md,
+    marginTop: SPACING.sm,
+  },
+  form: {
+    width: '100%',
+  },
+  error: {
+    color: COLORS.danger,
+    fontSize: FONT_SIZES.sm,
+    marginBottom: SPACING.md,
+    textAlign: 'center',
+  },
+  footer: {
+    flexDirection: 'row',
+    justifyContent: 'center',
+    marginTop: SPACING.lg,
+  },
+  footerText: {
+    color: COLORS.textSecondary,
+    fontSize: FONT_SIZES.sm,
+  },
+  link: {
+    color: COLORS.primary,
+    fontSize: FONT_SIZES.sm,
+    fontWeight: '600',
+  },
+});