Web still uses localStorage; Capacitor native app now routes
token/user/session-id through capacitor-secure-storage-plugin
(iOS Keychain, Android EncryptedSharedPreferences / Keystore).
A thin SecureStorage wrapper detects Capacitor at runtime and
falls back to localStorage elsewhere, keeping a single auth.js
codebase for both targets.
To activate on mobile: cd mobile && npm install && npx cap sync android
