Auto-detect Content-Type and Accept headers if enabled

Add AutoDetectHeaders option to RecAction config and handler. When enabled, automatically set Content-Type based on body content (JSON or XML) and default Accept to application/json if missing. Log warnings when headers are auto-detected. Improves robustness and makes header detection configurable.

src/ReC.Application/Common/Options/RecActionOptions.cs

@@ -3,4 +3,5 @@
 public class RecActionOptions
 {
     public bool UseHttp1ForNtlm { get; set; } = false;
+    public bool AutoDetectHeaders { get; set; } = false;
 }