fix(ml): model downloading improvements (#3988)

* handle ort `NoSuchFile` error, stricter file check

* keep exception order

machine-learning/app/models/clip.py

@@ -131,6 +131,10 @@ class CLIPEncoder(InferenceModel):
             os.remove(file)
         return True
 
+    @property
+    def cached(self) -> bool:
+        return (self.cache_dir / "textual.onnx").is_file() and (self.cache_dir / "visual.onnx").is_file()
+
 
 # same as `_transform_blob` without `_blob2image`
 def _transform_pil_image(n_px: int) -> Compose: