feat: add series support for book organization

API:
- Add /libraries/{id}/series endpoint to list series with book counts
- Add series filter to /books endpoint
- Fix SeriesItem to return first_book_id properly (using CTE with ROW_NUMBER)

Indexer:
- Parse series from parent folder name relative to library root
- Store series in database when indexing books

Backoffice:
- Add Books page with grid view, search, and pagination
- Add Series page showing series with cover images
- Add Library books page filtered by series
- Add book detail page
- Add Series column in libraries list with clickable link
- Create BookCard component for reusable book display
- Add CSS styles for books grid, series grid, and book details
- Add proxy API route for book cover images (fixing CORS issues)

Parser:
- Add series field to ParsedMetadata
- Extract series from file path relative to library root

Books without a parent folder are categorized as 'unclassified' series.

apps/api/src/openapi.rs

@@ -6,6 +6,7 @@ use utoipa::OpenApi;
     paths(
         crate::books::list_books,
         crate::books::get_book,
+        crate::books::list_series,
         crate::pages::get_page,
         crate::search::search_books,
         crate::index_jobs::enqueue_rebuild,
@@ -25,6 +26,7 @@ use utoipa::OpenApi;
             crate::books::BookItem,
             crate::books::BooksPage,
             crate::books::BookDetails,
+            crate::books::SeriesItem,
             crate::pages::PageQuery,
             crate::search::SearchQuery,
             crate::search::SearchResponse,