feat(books): édition des métadonnées livres et séries + champ authors multi-valeurs

- Nouveaux endpoints PATCH /books/:id et PATCH /libraries/:id/series/:name pour éditer les métadonnées
- GET /libraries/:id/series/:name/metadata pour récupérer les métadonnées de série
- Ajout du champ `authors` (Vec<String>) sur les structs Book/BookDetails
- 3 migrations : table series_metadata, colonne authors sur series_metadata et books
- Composants EditBookForm et EditSeriesForm dans le backoffice
- Routes API Next.js correspondantes

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

apps/backoffice/app/books/[id]/page.tsx

@@ -2,6 +2,7 @@ import { fetchLibraries, getBookCoverUrl, BookDto, apiFetch, ReadingStatus } fro
 import { BookPreview } from "../../components/BookPreview";
 import { ConvertButton } from "../../components/ConvertButton";
 import { MarkBookReadButton } from "../../components/MarkBookReadButton";
+import { EditBookForm } from "../../components/EditBookForm";
 import Image from "next/image";
 import Link from "next/link";
 import { notFound } from "next/navigation";
@@ -89,7 +90,10 @@ export default async function BookDetailPage({
 
         <div className="flex-1">
           <div className="bg-card rounded-xl shadow-sm border border-border p-6">
-            <h1 className="text-3xl font-bold text-foreground mb-2">{book.title}</h1>
+            <div className="flex items-start justify-between gap-4 mb-2">
+              <h1 className="text-3xl font-bold text-foreground">{book.title}</h1>
+              <EditBookForm book={book} />
+            </div>
             
             {book.author && (
               <p className="text-lg text-muted-foreground mb-4">by {book.author}</p>

apps/backoffice/app/books/page.tsx

@@ -40,6 +40,7 @@ export default async function BooksPage({
         kind: hit.kind,
         title: hit.title,
         author: hit.author,
+        authors: [],
         series: hit.series,
         volume: hit.volume,
         language: hit.language,