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/api/settings/search/resync/route.ts

@@ -0,0 +1,11 @@
+import { NextResponse } from "next/server";
+import { forceSearchResync } from "@/lib/api";
+
+export async function POST() {
+  try {
+    const data = await forceSearchResync();
+    return NextResponse.json(data);
+  } catch (error) {
+    return NextResponse.json({ error: "Failed to trigger search resync" }, { status: 500 });
+  }
+}