feat: fix author search, add edit modals, settings tabs & search resync

- Fix Meilisearch indexing to use authors[] array instead of scalar author field
- Join series_metadata to include series-level authors in search documents
- Configure searchable attributes (title, authors, series) in Meilisearch
- Convert EditSeriesForm and EditBookForm from inline forms to modals
- Add tabbed navigation (General / Integrations) to Settings page
- Add Force Search Resync button (POST /settings/search/resync)

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

apps/backoffice/app/books/page.tsx

@@ -39,8 +39,8 @@ export default async function BooksPage({
         library_id: hit.library_id,
         kind: hit.kind,
         title: hit.title,
-        author: hit.author,
-        authors: [],
+        author: hit.authors?.[0] ?? null,
+        authors: hit.authors ?? [],
         series: hit.series,
         volume: hit.volume,
         language: hit.language,