Replace placeholder toast with full metadata editor Alpine data component:
- Modal show/hide (showMetadataEditor, hideMetadataEditor)
- Accordion section toggle
- Cover upload via FileReader preview
- Cover generation via dynamic cover-generator import
- Cover removal with placeholder fallback
- saveMetadata(): collects form data, sends PUT as JSON or multipart
depending on whether a cover file is present
- Back button fix: skip overwriting sessionStorage back URL when
referrer is the current page (preserves navigation after page reload)
john-okeefe
1724bc0767