fix(ui): Harmonize spacing in library sub-pages

- Removed space-y-6 container wrapper
- Added explicit mb-6 margins on breadcrumb, h1, Card, and h2 elements
- Consistent spacing approach across all library pages

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

@@ -0,0 +1,95 @@
+import { fetchLibraries, fetchBooks, getBookCoverUrl, LibraryDto, BookDto } from "../../../../lib/api";
+import { BooksGrid, EmptyState } from "../../../components/BookCard";
+import { Card, Badge, Button, CursorPagination } from "../../../components/ui";
+import Link from "next/link";
+import { notFound } from "next/navigation";
+
+export const dynamic = "force-dynamic";
+
+export default async function LibraryBooksPage({
+  params,
+  searchParams
+}: {
+  params: Promise<{ id: string }>;
+  searchParams: Promise<{ [key: string]: string | string[] | undefined }>;
+}) {
+  const { id } = await params;
+  const searchParamsAwaited = await searchParams;
+  const cursor = typeof searchParamsAwaited.cursor === "string" ? searchParamsAwaited.cursor : undefined;
+  const series = typeof searchParamsAwaited.series === "string" ? searchParamsAwaited.series : undefined;
+  const limit = typeof searchParamsAwaited.limit === "string" ? parseInt(searchParamsAwaited.limit) : 20;
+  
+  const [library, booksPage] = await Promise.all([
+    fetchLibraries().then(libs => libs.find(l => l.id === id)),
+    fetchBooks(id, series, cursor, limit).catch(() => ({ 
+      items: [] as BookDto[], 
+      next_cursor: null 
+    }))
+  ]);
+
+  if (!library) {
+    notFound();
+  }
+
+  const books = booksPage.items.map(book => ({
+    ...book,
+    coverUrl: getBookCoverUrl(book.id)
+  }));
+  const nextCursor = booksPage.next_cursor;
+  
+  const seriesDisplayName = series === "unclassified" ? "Unclassified" : series;
+  const hasNextPage = !!nextCursor;
+  const hasPrevPage = !!cursor;
+
+  return (
+    <>
+      <div className="mb-6">
+        <Link href="/libraries" className="text-sm text-muted hover:text-primary transition-colors">← Back to libraries</Link>
+      </div>
+
+      <h1 className="text-3xl font-bold text-foreground flex items-center gap-3 mb-6">
+        <svg className="w-8 h-8 text-success" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 6.253v13m0-13C10.832 5.477 9.246 5 7.5 5S4.168 5.477 3 6.253v13C4.168 18.477 5.754 18 7.5 18s3.332.477 4.5 1.253m0-13C13.168 5.477 14.754 5 16.5 5c1.747 0 3.332.477 4.5 1.253v13C19.832 18.477 18.247 18 16.5 18c-1.746 0-3.332.477-4.5 1.253" /></svg>
+        {library.name}
+      </h1>
+      
+      <Card className="mb-6">
+        <div className="flex flex-wrap items-center gap-3 text-sm">
+          <code className="text-xs font-mono text-muted bg-muted/10 px-2 py-1 rounded">{library.root_path}</code>
+          <span className="text-muted">|</span>
+          <span className="text-foreground">{library.book_count} book{library.book_count !== 1 ? 's' : ''}</span>
+          <span className="text-muted">|</span>
+          <Badge variant={library.enabled ? "success" : "muted"}>
+            {library.enabled ? "Enabled" : "Disabled"}
+          </Badge>
+        </div>
+      </Card>
+
+      <div className="flex items-center gap-4 mb-6">
+        <h2 className="text-xl font-semibold text-foreground">
+          {series ? `Books in "${seriesDisplayName}"` : "All Books"}
+        </h2>
+        {series && (
+          <Link href={`/libraries/${id}/books`} className="text-sm text-primary hover:text-primary/80">
+            View all
+          </Link>
+        )}
+      </div>
+
+      {books.length > 0 ? (
+        <>
+          <BooksGrid books={books} />
+          
+          <CursorPagination
+            hasNextPage={hasNextPage}
+            hasPrevPage={hasPrevPage}
+            pageSize={limit}
+            currentCount={books.length}
+            nextCursor={nextCursor}
+          />
+        </>
+      ) : (
+        <EmptyState message={series ? `No books in series "${seriesDisplayName}"` : "No books in this library yet"} />
+      )}
+    </>
+  );
+}