feat(backoffice): add reading progress management, series page, and live search

- API: add POST /series/mark-read to batch mark all books in a series
- API: add GET /series cross-library endpoint with search, library and status filters
- API: add library_id to SeriesItem response
- Backoffice: mark book as read/unread button on book detail page
- Backoffice: mark series as read/unread button on series cards
- Backoffice: new /series top-level page with search and filters
- Backoffice: new /libraries/[id]/series/[name] series detail page
- Backoffice: opacity on fully read books and series cards
- Backoffice: live search with debounce on books and series pages
- Backoffice: reading status filter on books and series pages
- Fix $2 -> $1 parameter binding in mark-series-read SQL

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/backoffice/app/components/BookCard.tsx

@@ -61,10 +61,12 @@ export function BookCard({ book, readingStatus }: BookCardProps) {
   const status = readingStatus ?? book.reading_status;
   const overlay = status ? readingStatusOverlay[status] : null;
 
+  const isRead = status === "read";
+
   return (
     <Link
       href={`/books/${book.id}`}
-      className="group block bg-card rounded-xl border border-border/60 shadow-sm hover:shadow-md hover:-translate-y-1 transition-all duration-200 overflow-hidden"
+      className={`group block bg-card rounded-xl border border-border/60 shadow-sm hover:shadow-md hover:-translate-y-1 transition-all duration-200 overflow-hidden ${isRead ? "opacity-50" : ""}`}
     >
       <div className="relative">
         <BookImage