Added Last Name display and made it editable

frontend/pweb/lib/widgets/drawer/avatar.dart

@@ -50,7 +50,7 @@ class AccountAvatar extends StatelessWidget {
 
     final loc = AppLocalizations.of(context)!;
     return UserAccountsDrawerHeader(
-      accountName: Text(provider.account?.describable.name ?? loc.userNamePlaceholder),
+      accountName: Text(provider.account?.fullName ?? loc.userNamePlaceholder),
       accountEmail: Text(provider.account?.login ?? loc.usernameHint),
       currentAccountPicture: avatar,
     );

frontend/pweb/lib/widgets/sidebar/sidebar.dart

@@ -32,7 +32,7 @@ class PayoutSidebar extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final accountName = context.select<AccountProvider, String?>(
-      (provider) => provider.account?.describable.name,
+      (provider) => provider.account?.fullName,
     );
     final accountAvatar = context.select<AccountProvider, String?>(
       (provider) => provider.account?.avatarUrl,