fix chart rec

app.py

@@ -101,7 +101,7 @@ def _call_api(api_url: str, file_path: str, use_layout_detection: bool,
             raise ValueError("Please select a recognition type.")
         payload["promptLabel"] = prompt_label.strip().lower()
     if use_layout_detection and use_chart_recognition:
-        payload["use_chart_recognition"] = True
+        payload["useChartRecognition"] = True
 
     try:
         # 关键改动：带上 headers