redesigned payment page + a lot of fixes

frontend/pweb/lib/controllers/auth/account_loader.dart

@@ -0,0 +1,63 @@
+import 'package:flutter/foundation.dart';
+
+import 'package:pshared/models/auth/state.dart';
+import 'package:pshared/provider/account.dart';
+
+import 'package:pweb/models/account/account_loader.dart';
+
+
+class AccountLoaderController extends ChangeNotifier {
+  AccountProvider? _provider;
+  AuthState? _handledState;
+  AccountLoaderAction? _action;
+  Object? _error;
+
+  AccountLoaderAction? get action => _action;
+  Object? get error => _error;
+
+  void update(AccountProvider provider) {
+    if (identical(_provider, provider)) return;
+    _provider?.removeListener(_handleProviderChanged);
+    _provider = provider;
+    _provider?.addListener(_handleProviderChanged);
+    _evaluate(provider);
+  }
+
+  AccountLoaderAction? consumeAction() {
+    final action = _action;
+    _action = null;
+    return action;
+  }
+
+  void _handleProviderChanged() {
+    final provider = _provider;
+    if (provider == null) return;
+    _evaluate(provider);
+  }
+
+  void _evaluate(AccountProvider provider) {
+    if (_handledState == provider.authState) return;
+    _handledState = provider.authState;
+
+    switch (provider.authState) {
+      case AuthState.error:
+        _error = provider.error ?? Exception('Authorization failed');
+        _action = AccountLoaderAction.showErrorAndGoToLogin;
+        notifyListeners();
+        break;
+      case AuthState.empty:
+        _error = null;
+        _action = AccountLoaderAction.goToLogin;
+        notifyListeners();
+        break;
+      default:
+        break;
+    }
+  }
+
+  @override
+  void dispose() {
+    _provider?.removeListener(_handleProviderChanged);
+    super.dispose();
+  }
+}