Fix KeyError when 'hashes', 'name', or 'model' fields are missing from
Civitai API responses. Use .get() with defaults instead of direct dict
access in:
- LoraMetadata.from_civitai_info()
- CheckpointMetadata.from_civitai_info()
- EmbeddingMetadata.from_civitai_info()
- RecipeScanner._get_hash_from_civitai()
- DownloadManager._process_download()
Fixes#820