layout: fix grid cover image height in crop mode (#1537)

Support setting arbitrary columns with custom UI css:
```
.bookshelf-items {
  grid-template-columns: repeat(3, minmax(0, 1fr)) !important;
}
```

apps/readest-app/src/app/library/components/BookItem.tsx

@@ -62,6 +62,7 @@ const BookItem: React.FC<BookItemProps> = ({
       <div
         className={clsx(
           'relative flex aspect-[28/41] items-center justify-center',
+          coverFit === 'crop' && 'overflow-hidden shadow-md',
           mode === 'list' && 'min-w-20',
         )}
       >

apps/readest-app/src/app/library/components/Bookshelf.tsx

@@ -285,7 +285,7 @@ const Bookshelf: React.FC<BookshelfProps> = ({
     <div className='bookshelf'>
       <div
         className={clsx(
-          'transform-wrapper',
+          'bookshelf-items transform-wrapper',
           viewMode === 'grid' && 'grid flex-1 grid-cols-3 gap-x-4 px-4 sm:gap-x-0 sm:px-2',
           viewMode === 'grid' && 'sm:grid-cols-4 md:grid-cols-6 xl:grid-cols-8 2xl:grid-cols-12',
           viewMode === 'list' && 'flex flex-col',

apps/readest-app/src/components/BookCover.tsx

@@ -40,7 +40,7 @@ const BookCover: React.FC<BookCoverProps> = ({
           src={book.coverImageUrl!}
           alt={book.title}
           fill={true}
-          className={clsx('crop-cover-img object-cover shadow-md', imageClassName)}
+          className={clsx('crop-cover-img object-cover', imageClassName)}
           onError={handleImageError}
         />
       ) : (