Initial commit: Expo app with Better Auth integration

- Complete Expo React Native app setup with TypeScript
- Better Auth authentication system integration
- Secure storage implementation for session tokens
- Authentication flow with login/logout functionality
- API client configuration for backend communication
- Responsive UI components with themed styling
- Expo Router navigation setup
- Development configuration and scripts

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

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

app/(auth)/_layout.tsx

@@ -0,0 +1,15 @@
+import { Stack } from "expo-router";
+
+export default function AuthLayout() {
+  return (
+    <Stack
+      screenOptions={{
+        headerShown: false,
+        contentStyle: { backgroundColor: "#fff" },
+      }}
+    >
+      <Stack.Screen name="login" />
+      <Stack.Screen name="register" />
+    </Stack>
+  );
+}