fix: Handle missing Civitai API response fields gracefully

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

py/services/download_manager.py

@@ -496,7 +496,9 @@ class DownloadManager:
                 return {"success": False, "error": "No mirror URL found"}
 
             # 3. Prepare download
-            file_name = file_info["name"]
+            file_name = file_info.get("name", "")
+            if not file_name:
+                return {"success": False, "error": "No filename found in file info"}
             save_path = os.path.join(save_dir, file_name)
 
             # 5. Prepare metadata based on model type