Refactor error handling to use ApiClientHelper

Replaced the private ReadErrorAsync method in LayoutApiClient with calls to ApiClientHelper.ReadErrorAsync, centralizing error handling logic for improved consistency and reuse.

DbFirst.BlazorWebApp/Services/LayoutApiClient.cs

@@ -31,7 +31,7 @@ public class LayoutApiClient
         var response = await _httpClient.PostAsJsonAsync(Endpoint, dto);
         if (!response.IsSuccessStatusCode)
         {
-            var detail = await ReadErrorAsync(response);
+            var detail = await ApiClientHelper.ReadErrorAsync(response);
             throw new InvalidOperationException(detail);
         }
 
@@ -39,17 +39,6 @@ public class LayoutApiClient
         return payload ?? dto;
     }
 
-    private static async Task<string> ReadErrorAsync(HttpResponseMessage response)
-    {
-        var body = await response.Content.ReadAsStringAsync();
-        if (!string.IsNullOrWhiteSpace(body))
-        {
-            return body;
-        }
-
-        return $"{(int)response.StatusCode} {response.ReasonPhrase}".Trim();
-    }
-
     public async Task DeleteAsync(string layoutType, string layoutKey, string userName)
     {
         var url = $"{Endpoint}?layoutType={Uri.EscapeDataString(layoutType)}&layoutKey={Uri.EscapeDataString(layoutKey)}&userName={Uri.EscapeDataString(userName)}";