fixed guardian login edge cases and misleading placeholders on failed loads

lib/view/login/widgets/guardian_login_card.dart

@@ -158,7 +158,7 @@ class _GuardianLoginCardState extends State<GuardianLoginCard> {
   Widget _buildCodeStep(BuildContext context) {
     final theme = Theme.of(context);
     final pending = _controller.pending!;
-    final remaining = pending.resendAvailableAt.difference(DateTime.now());
+    final remaining = _controller.resendCooldown();
     return Form(
       key: _codeFormKey,
       child: LoginCardFrame(

lib/view/login/widgets/login_audience_card.dart

@@ -14,7 +14,7 @@ class LoginAudienceCard extends StatelessWidget {
   @override
   Widget build(BuildContext context) => LoginCardFrame(
     title: 'Anmelden',
-    hint: 'Bite wähle deine Anmeldemethode',
+    hint: 'Bitte wähle deine Anmeldemethode',
     children: [
       _AudienceButton(
         key: const Key('login-audience-school'),