Add retry logic and fallback mechanism to prompt generation. When OpenWebUI
fails, the system now attempts a second try before falling back to OpenRouter.
Proper error handling and logging have been added throughout the prompt
generation flow to ensure more reliable operation.
Previously, if a user favorited a newly generated image (named 'image.png'), the favorite status would be lost once the image was automatically renamed to its final timestamped filename.
This change modifies the renaming logic to check the `favourites.json` file. If 'image.png' is found, its entry is updated with the new filename, ensuring the favorite status is preserved.
