fix(backend): normalize Windows backslash paths on Linux CI

Path("models\\yolo.pt") on Linux treats backslash as a literal filename
character, not a separator. Explicitly replace backslashes before Path()
construction so _normalize_model_path works cross-platform. Fixes the
only failing CI test (test_normalize_model_path).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: alireza787b

src/classes/backends/ultralytics_backend.py

@@ -354,7 +354,9 @@ def _normalize_device_preference(device: str) -> str:
 
     @staticmethod
     def _normalize_model_path(model_path: str) -> str:
-        return str(Path(model_path).as_posix())
+        # Replace Windows backslashes before Path() so Linux doesn't treat
+        # them as literal filename characters.
+        return str(Path(model_path.replace("\\", "/")).as_posix())
 
     @staticmethod
     def _is_valid_ncnn_dir(model_path: str) -> bool: