Introduce StartRouter to gate first run with onboarding. Persist state in
SharedPreferences (onboarded_v1). Add WelcomeScreen, a 3-step
OnboardingFlow, and a SignInScreen placeholder with Apple/Google buttons
and "coming soon" toasts plus continue as guest.
Apply new AppThemes (light/dark, high-contrast option) built from design
tokens and wire into MaterialApp (theme/darkTheme, system mode). Add
ThemeProvider to persist ThemeMode and high-contrast flags (not yet
hooked into the tree).
Add EN/MS i18n strings for welcome, onboarding, auth, and CTAs. Include
assets/tokens/design-tokens.json for design tooling parity.
Zahar
8d69c9c846