Refactor metadata handling to use unified provider system

- Replaced direct usage of Civitai client with a fallback metadata provider across all recipe parsers.
- Updated metadata service to improve initialization and error handling.
- Enhanced download manager to utilize a downloader service for file operations.
- Improved recipe scanner to fetch model information through the new metadata provider.
- Updated utility functions to streamline image downloading and processing.
- Added comprehensive logging and error handling for better debugging and reliability.
- Introduced `get_default_metadata_provider()` for simplified access to the default provider.
- Ensured backward compatibility with existing APIs and workflows.

py/services/model_scanner.py

@@ -730,11 +730,10 @@ class ModelScanner:
             
             if needs_metadata_update and model_id:
                 logger.debug(f"Fetching missing metadata for {file_path} with model ID {model_id}")
-                from ..services.civitai_client import CivitaiClient
-                client = CivitaiClient()
+                from ..services.metadata_service import get_default_metadata_provider
+                metadata_provider = await get_default_metadata_provider()
                 
-                model_metadata, status_code = await client.get_model_metadata(model_id)
-                await client.close()
+                model_metadata, status_code = await metadata_provider.get_model_metadata(model_id)
                 
                 if status_code == 404:
                     logger.warning(f"Model {model_id} appears to be deleted from Civitai (404 response)")