Debug: Add loading and error screens to diagnose startup issues

App.test.tsx

@@ -0,0 +1,32 @@
+import React from 'react';
+import { View, Text, StyleSheet } from 'react-native';
+
+export default function App() {
+  return (
+    <View style={styles.container}>
+      <Text style={styles.text}>✅ WalletTracker fonctionne !</Text>
+      <Text style={styles.subtext}>Si vous voyez ce message, l'app charge correctement.</Text>
+    </View>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+    justifyContent: 'center',
+    alignItems: 'center',
+    backgroundColor: '#F8F9FA'
+  },
+  text: {
+    fontSize: 24,
+    fontWeight: 'bold',
+    color: '#333',
+    marginBottom: 16
+  },
+  subtext: {
+    fontSize: 16,
+    color: '#666',
+    textAlign: 'center',
+    paddingHorizontal: 32
+  }
+});