feat(wechat): Improve template message response handling with logging

- Add response content logging for debugging template message sends
- Handle empty response cases with explicit null check and warning log
- Replace ReadFromJsonAsync with manual deserialization for better error visibility
- Ensure service account template messages are properly validated before processing

server/src/XiangYi.Infrastructure/WeChat/WeChatService.cs

@@ -452,7 +452,17 @@ public class WeChatService : IWeChatService
             }
 
             var response = await _httpClient.PostAsJsonAsync(url, requestBody);
-            var result = await response.Content.ReadFromJsonAsync<WeChatApiResponse>();
+            var responseContent = await response.Content.ReadAsStringAsync();
+
+            _logger.LogInformation("发送服务号模板消息响应: {Response}", responseContent);
+
+            if (string.IsNullOrWhiteSpace(responseContent))
+            {
+                _logger.LogWarning("发送服务号模板消息失败: 微信返回空响应");
+                return false;
+            }
+
+            var result = System.Text.Json.JsonSerializer.Deserialize<WeChatApiResponse>(responseContent);
 
             if (result?.ErrCode != 0)
             {