fix(metadata): rename model_type to sub_type and add embedding subtype, see #797

- Change `model_type` field to `sub_type` for checkpoint models to improve naming consistency
- Add `sub_type="embedding"` for embedding models to properly categorize model subtypes
- Maintain backward compatibility with existing metadata structure

py/utils/metadata_manager.py

@@ -223,7 +223,7 @@ class MetadataManager:
                     preview_url=normalize_path(preview_url),
                     tags=[],
                     modelDescription="",
-                    model_type="checkpoint",
+                    sub_type="checkpoint",
                     from_civitai=True
                 )
             elif model_class.__name__ == "EmbeddingMetadata":
@@ -238,6 +238,7 @@ class MetadataManager:
                     preview_url=normalize_path(preview_url),
                     tags=[],
                     modelDescription="",
+                    sub_type="embedding",
                     from_civitai=True
                 )
             else:  # Default to LoraMetadata