fix: address code review findings for mobile app (FRE-4572)

P0 fixes:
- Replace crypto.randomUUID() with uuid v4 (not available in RN)
- Replace Platform.Version with expo-device osVersion
- Fix auth navigation types, remove unused App route

P1 fixes:
- Push notification handler respects user preferences (useRef pattern)
- Fix stale closure: use zustand subscribe + useRef for live preferences
- Add retry logging for device registration failures
- Replace emoji tab icons with @expo/vector-icons Ionicons
- Document API integration TODOs in all local-only stores

P2 fixes:
- Add __DEV__ global declaration (global.d.ts)
- Fix package.json main field to expo/AppEntry.js
- Add retry logging for push device registration
- Add z-index/elevation to LoadingOverlay
- Add visual indicator to EmptyState icon

P3 fixes:
- Type navigation with NavigationProp<RootStackParamList>
- Move getSeverityColor to theme.ts (single source of truth)
- Add useMemo for SpamShield filter computations
- Verified usesNonExemptEncryption: false is correct for expo-secure-store

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

packages/mobile/src/screens/auth/LoginScreen.tsx

@@ -1,6 +1,6 @@
 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 { useNavigation, NavigationProp } from '@react-navigation/native';
 import { useAuthStore } from '@/store/authStore';
 import { Button, Input } from '@/components';
 import { COLORS, FONT_SIZES, SPACING } from '@/constants/theme';
@@ -8,15 +8,11 @@ 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 navigation = useNavigation<NavigationProp<RootStackParamList>>();
+  const { login, isLoading, clearError } = useAuthStore();
 
   const [email, setEmail] = useState('');
   const [password, setPassword] = useState('');