refactor(cards): bookshelf SSR through the builder — badges return to the bookshelf

The ExecuteSearch-driven bookshelf page fed SearchMediaItemsUnifiedRow
— which HAS FormatGroup and LibraryTypeName — into a bare 4-field
literal that dropped both, so bookshelf cards lost the media-type
badge the shelf once had. BookCardsFromUnified emits badge/format on
this surface (card-marking rides on; the SQL column strategy means
zero extra queries). audiobook shelves regain the corner glyph.

internal/router/frontend.go

@@ -373,17 +373,7 @@ func registerFrontendRoutes(cfg *Config) {
 			if err != nil {
 				log.Printf("ExecuteSearch failed: %v", err)
 			} else {
-				bookInfoList = make([]handlers.BookInfo, len(results))
-				for i, book := range results {
-					bookUUID, _ := uuid.FromBytes(book.ID.Bytes[0:16])
-					bookLibUUID, _ := uuid.FromBytes(book.LibraryID.Bytes[0:16])
-					bookInfoList[i] = handlers.BookInfo{
-						MediaItemID:    bookUUID.String(),
-						Title:          book.Title,
-						Author:         textToString(book.Author),
-						CoverImagePath: utils.ResolveMediaURL(pgtype.UUID{Bytes: bookLibUUID, Valid: true}, book.CoverImagePath),
-					}
-				}
+				bookInfoList = handlers.BookCardsFromUnified(results)
 			}
 		}