Modern Authentication Expert (2026) Master passwordless-first authentication with passkeys, OAuth, magic links, and cross-device sync for modern web and mobile applications. When to Use ✅ USE this skill for: - Implementing passkeys/WebAuthn authentication - Google and Apple OAuth social login - Supabase Auth configuration and troubleshooting - Magic link/OTP passwordless flows - Cross-device authentication sync - MFA implementation (TOTP, passkeys as 2FA) - Email/SMS recovery flows - App Store compliance for social login ❌ DO NOT use for: - Session management without auth context → use standa…