Rich descriptions and author photos

Rich descriptions - entity descriptions now support bold, italic, and cross-reference links to other entities. Links are validated and rendered with entity-coloured text on public pages.

Author photo picker - when creating or editing an author, choose from up to 6 photos fetched from Open Library. A "Refresh" button fetches fresh options.

Image loading - book covers and author photos now fade in smoothly with loading spinners, replacing the previous instant-load flash.

ISBN lookup improvements - better detection of original publication years, duplicate book detection by ISBN, and cleaner title formatting.

Curator forms modernised - all 12 create/edit forms now use shared validation hooks, 9 inline drawer forms extracted into reusable components, and character view pages decomposed into focused section components.