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/downloader.py

@@ -276,6 +276,10 @@ class Downloader:
                         
                         while rename_attempt < max_rename_attempts and not rename_success:
                             try:
+                                # If the destination file exists, remove it first (Windows safe)
+                                if os.path.exists(save_path):
+                                    os.remove(save_path)
+
                                 os.rename(part_path, save_path)
                                 rename_success = True
                             except PermissionError as e: