fix(web): правильный парсинг query string для ?register=1

Заменен Navigation.Uri.Contains() на QueryHelpers.ParseQuery
для корректного определения параметра register без ложных
срабатываний на подстроки (например, register=10).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/GmRelay.Web/Components/Pages/PublicSession.razor

@@ -138,7 +138,11 @@ else if (session is not null)
         var authState = await AuthStateProvider.GetAuthenticationStateAsync();
         isAuthenticated = authState.User.Identity?.IsAuthenticated ?? false;
 
-        if (session is not null && Navigation.Uri.Contains("register=1") && session.AllowDirectRegistration)
+        var uri = Navigation.ToAbsoluteUri(Navigation.Uri);
+        var query = Microsoft.AspNetCore.WebUtilities.QueryHelpers.ParseQuery(uri.Query);
+        var shouldRegister = query.TryGetValue("register", out var val) && val == "1";
+
+        if (session is not null && shouldRegister && session.AllowDirectRegistration)
         {
             if (isAuthenticated && authState.User.TryGetPlatformIdentity(out var platform, out var externalUserId))
             {