Auth State Notifier

Global StateNotifier exposing the (isLoggedIn, role) tuple. On construction it inspects persisted tokens and resolves the initial role: seller token present → freelancer, customer-only → client, otherwise guest.

1. App boot → AuthStateNotifier ctor calls _loadInitialState.
2. _loadInitialState reads isLoggedIn from SharedPreferences and inspects hasSellerRole().
3. switchRole(newRole) is invoked when the user toggles between client and freelancer in the UI — only succeeds if a token for that role exists.
4. logout() clears the session, deletes the FCM token, and resets state to AuthState(false, guest).

• AuthState overrides == and hashCode so refreshAuthState() does not re-trigger watchers when the (isLoggedIn, role) tuple is unchanged — without this, /store/customers/me would fetch twice on home boot (see explicit comment in code).
• logout swallows NotificationService.deleteToken errors when FCM is not initialized.
• switchRole silently no-ops if the requested role has no stored token — the UI must not assume the call succeeded.

• lib/src/core/services/auth_storage.dart:257 // authStateProvider
• lib/src/core/services/auth_storage.dart:263 // AuthStateNotifier
• lib/src/core/services/auth_storage.dart:328 // AuthState equality override

Lives in auth_storage.dart alongside the storage service rather than under features/auth — it is consumed across the whole app (settings, profile, navigation) so its DI scope is core.