feat: implement form validation helpers and integrate field-level validation in agent profile screen, reset auth error suppression on login, and clean up home header UI.

lib/features/auth/presentation/providers/auth_provider.dart

@@ -137,6 +137,10 @@ class AuthNotifier extends StateNotifier<AuthState> {
     required String password,
     String? loginRole,
   }) async {
+    // Reset suppressAuthErrors in case a prior logout left it enabled —
+    // otherwise the 401 interceptor rejects errors unwrapped and we lose
+    // the backend's message (e.g. role-mismatch), falling back to generic.
+    ApiClient.suppressAuthErrors = false;
     state = state.copyWith(
       status: AuthStatus.loading,
       errorMessage: null,