App works on IPv6-only networks

Apple requires all iOS apps to work on IPv6-only networks and tests this during review using an IPv6 NAT64 hotspot. Hardcoded IPv4 addresses (e.g., 192.168.1.100 that leaked from a development config) break immediately on IPv6-only networks because those addresses cannot be reached. This is a direct rejection cause for iOS submissions. ISO 25010:2011 operational-readiness requires software to function in the range of environments it claims to support — IPv6-only networks are widespread in cellular carrier environments and Apple's own review lab.

Replace every hardcoded IPv4 address in production configuration with a hostname.

// src/config/api.ts
// Wrong — fails on IPv6-only networks:
export const API_URL = 'http://192.168.1.100:3000';

// Correct — DNS resolves to IPv4 or IPv6 as needed:
export const API_URL = process.env.EXPO_PUBLIC_API_URL ?? 'https://api.yourdomain.com';

To test IPv6 compatibility on macOS: go to System Settings > Sharing > Internet Sharing, share your Ethernet connection over Wi-Fi, enable "Enable IPv6" in the Wi-Fi options. Connect your test device to this hotspot and run the app. Any hardcoded IPv4 URL will fail immediately.