Refactor Export PDF Generation Task

[susilnem]

Description

Currently, the generate_url Celery task handles:

• Playwright setup (build_storage_state, PDF rendering)
• PDF generation and saving
• File naming using title and export type
• Export status updates and error handling

Goals for Refactor:

• Centralize filename and title generation inside the task.
• Remove duplication between serializer and task.
• Improve readability and maintainability.
• Consider renaming the task to something more descriptive, e.g., generate_export_pdf.
• Enhance error handling and logging.

References:

• ExportSerializer
• (generate_url) task