Fix syntax error in try-except block

- Fixed malformed nested try-except in yolo_detect_signatures
- Added proper except block for fallback PyTorch inference
- Renamed exception variable to avoid shadowing

app.py

@@ -213,10 +213,10 @@ def yolo_detect_signatures(
                 classes = r.boxes.cls.cpu().numpy().astype(int)
                 for b, s, c in zip(xyxy, scores, classes):
                     boxes.append((b, float(s), int(c)))
-        return boxes
-    except Exception as e:
-        print(f"YOLO detection failed: {e}")
-        return []
+            return boxes
+        except Exception as fallback_error:
+            print(f"PyTorch fallback also failed: {fallback_error}")
+            return []
 
 
 def annotate_signature_boxes_on_pil(img_pil: Image.Image, boxes: List[Tuple[np.ndarray, float, int]]) -> Image.Image: