fix(wechat): 验签接口支持 HEAD 并避免配置异常返回非 200

微信后台/探活对 HEAD 会收到 405；读取 wechat_mp 配置异常时改为 HTTP 200 + error，与 WMS 行为一致。

Co-authored-by: Cursor <cursoragent@cursor.com>

src/SimpleAdmin.Api.IntegrationTests/WeChatRouteIntegrationTests.cs

@@ -46,6 +46,17 @@ public class WeChatRouteIntegrationTests
         (await response.Content.ReadAsStringAsync()).Should().Be(echostr);
     }
 
+    [Fact]
+    public async Task WeChatValidateLegacy_Head_ShouldReturn200()
+    {
+        await using var host = await SimpleAdminApiTestHost.CreateAsync(configureServices: ConfigureWeChatFallback);
+
+        var request = new HttpRequestMessage(HttpMethod.Head, "/apiwechat/verification");
+        var response = await host.Client.SendAsync(request);
+
+        response.StatusCode.Should().Be(HttpStatusCode.OK);
+    }
+
     private static void ConfigureWeChatFallback(IServiceCollection services)
     {
         services.PostConfigure<WeChatMpOptions>(options =>

src/SimpleAdmin.Api/Auth/AuthService.WeChatMp.cs

@@ -27,6 +27,7 @@ public partial class AuthService
     /// </summary>
     [AllowAnonymous]
     [HttpGet("/apiwechat/verification")]
+    [HttpHead("/apiwechat/verification")]
     [Produces("text/plain")]
     [ApiExplorerSettings(GroupName = "WeChat")]
     public async Task<ContentResult> WeChatValidateLegacyAsync(
@@ -35,10 +36,36 @@ public partial class AuthService
         [FromQuery] string? nonce,
         [FromQuery] string? echostr,
         CancellationToken cancellationToken = default)
+    {
+        if (string.Equals(
+                httpContextAccessor.HttpContext?.Request.Method,
+                HttpMethods.Head,
+                StringComparison.OrdinalIgnoreCase))
+        {
+            return WeChatMpCallbackSupport.HeadOk();
+        }
+
+        return await WeChatValidateCoreAsync(signature, timestamp, nonce, echostr, cancellationToken);
+    }
+
+    private async Task<ContentResult> WeChatValidateCoreAsync(
+        string? signature,
+        string? timestamp,
+        string? nonce,
+        string? echostr,
+        CancellationToken cancellationToken)
+    {
+        try
         {
             var options = await WeChatMpConfigProvider.GetAsync(cancellationToken);
             return WeChatMpCallbackSupport.Validate(options, signature, timestamp, nonce, echostr);
         }
+        catch (Exception ex)
+        {
+            WeChatLogger.LogWarning(ex, "微信公众号验签读取配置失败");
+            return WeChatMpCallbackSupport.PlainError();
+        }
+    }
 
     /// <summary>
     /// 微信服务器接入验签。

src/SimpleAdmin.Api/WeChat/WeChatMpCallbackSupport.cs

@@ -17,7 +17,7 @@ internal static class WeChatMpCallbackSupport
         // 微信服务器要求 HTTP 200 + 纯文本 echostr，不可抛 BusinessException（会变成 JSON 非 200）
         if (string.IsNullOrWhiteSpace(options.Token))
         {
-            return PlainText("error");
+            return PlainError();
         }
 
         if (string.IsNullOrWhiteSpace(signature)
@@ -25,13 +25,19 @@ internal static class WeChatMpCallbackSupport
             || string.IsNullOrWhiteSpace(nonce)
             || string.IsNullOrWhiteSpace(echostr))
         {
-            return PlainText("error");
+            return PlainError();
         }
 
         var valid = WeChatSignatureHelper.Validate(options.Token, timestamp, nonce, signature);
         return PlainText(valid ? echostr : "error");
     }
 
+    /// <summary>微信或探活可能发 HEAD，须返回 200（WMS/Spring 默认支持）。</summary>
+    public static ContentResult HeadOk() =>
+        new() { Content = string.Empty, ContentType = "text/plain; charset=utf-8", StatusCode = StatusCodes.Status200OK };
+
+    public static ContentResult PlainError() => PlainText("error");
+
     public static async Task<ContentResult> HandleMessageAsync(
         WeChatMpOptions options,
         IWeChatEventHandler eventHandler,