T407551-Add author form
Developed a comprehensive "Add Author" form page that aligns with the Author class structure in pdclasses.py, enabling users to input author information that corresponds to Wikidata properties retrieved by the application.
Key features:
- The form fields were designed to mirror the attributes of the Author class
- Real-time image preview with 800ms debounce to prevent excessive requests
- Handling different image states e.g. Error message display when image fails to load & loading states.
- Basic form validation for now (can be expanded on later).

