fix: reserve detail cover box and async-decode list/shelf covers

- The manga detail desktop overview cover had no reserved aspect-ratio, so
  the meta column reflowed when it decoded. Give .cover aspect-ratio: 2/3 +
  object-fit: cover (mirrors MangaCard).
- Add decoding="async" to the detail hero/overview covers and the list/shelf
  covers (bookmarks, history, continue-reading, collections, tagged rows) so
  decode stays off the main thread — previously only MangaCard had it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.115.1",
+  "version": "0.115.2",
   "private": true,
   "type": "module",
   "scripts": {

frontend/src/lib/components/BookmarkList.svelte

@@ -23,6 +23,7 @@
                         alt=""
                         class="cover"
                         loading="lazy"
+                        decoding="async"
                     />
                 {:else}
                     <div class="cover cover-placeholder">

frontend/src/lib/components/CollectionsGrid.svelte

@@ -26,6 +26,7 @@
                                 alt=""
                                 class="collage-cover"
                                 loading="lazy"
+                                decoding="async"
                             />
                         {/each}
                     {/if}

frontend/src/lib/components/ContinueReadingShelf.svelte

@@ -51,6 +51,7 @@
                                 alt=""
                                 class="cover"
                                 loading="lazy"
+                                decoding="async"
                             />
                         {:else}
                             <span class="cover cover-placeholder">

frontend/src/lib/components/HistoryList.svelte

@@ -89,6 +89,7 @@
                             alt=""
                             class="cover"
                             loading="lazy"
+                            decoding="async"
                         />
                     {:else}
                         <div class="cover cover-placeholder">

frontend/src/lib/components/HistoryList.svelte.test.ts

@@ -29,6 +29,16 @@ describe('HistoryList', () => {
         expect(cont.getAttribute('href')).toBe('/manga/m1/chapter/c9');
     });
 
+    it('renders covers with lazy loading and async decode', () => {
+        render(HistoryList, {
+            props: { entries: [entry({ manga_cover_image_path: 'mangas/m1/cover.jpg' })] }
+        });
+        const img = document.querySelector('img.cover') as HTMLImageElement;
+        expect(img).not.toBeNull();
+        expect(img.getAttribute('loading')).toBe('lazy');
+        expect(img.getAttribute('decoding')).toBe('async');
+    });
+
     it('appends the page number to the continue line only past page 1', () => {
         // The page suffix is a separate text node from "Continue Chapter N",
         // so assert against the link's normalized text rather than getByText.

frontend/src/lib/components/TaggedChapterRow.svelte

@@ -27,7 +27,7 @@
 <li class="row" data-testid={testid}>
     <a {href} class="cover-link" aria-hidden="true" tabindex="-1">
         {#if primaryCover}
-            <img src={fileUrl(primaryCover)} alt="" class="cover" loading="lazy" />
+            <img src={fileUrl(primaryCover)} alt="" class="cover" loading="lazy" decoding="async" />
         {:else}
             <div class="cover cover-placeholder"></div>
         {/if}
@@ -46,7 +46,7 @@
         {#if item.sample_storage_keys.length > 1}
             <div class="samples">
                 {#each item.sample_storage_keys.slice(1) as key (key)}
-                    <img src={fileUrl(key)} alt="" class="sample" loading="lazy" />
+                    <img src={fileUrl(key)} alt="" class="sample" loading="lazy" decoding="async" />
                 {/each}
             </div>
         {/if}

frontend/src/lib/components/TaggedMangaRow.svelte

@@ -36,7 +36,7 @@
 <li class="row" data-testid={testid}>
     <a {href} class="cover-link" aria-hidden="true" tabindex="-1">
         {#if primaryCover}
-            <img src={fileUrl(primaryCover)} alt="" class="cover" loading="lazy" />
+            <img src={fileUrl(primaryCover)} alt="" class="cover" loading="lazy" decoding="async" />
         {:else}
             <div class="cover cover-placeholder"></div>
         {/if}
@@ -50,7 +50,7 @@
         {#if sampleStrip.length > 0}
             <div class="samples">
                 {#each sampleStrip as key (key)}
-                    <img src={fileUrl(key)} alt="" class="sample" loading="lazy" />
+                    <img src={fileUrl(key)} alt="" class="sample" loading="lazy" decoding="async" />
                 {/each}
             </div>
         {/if}

frontend/src/lib/components/TaggedPageRow.svelte

@@ -35,6 +35,7 @@
             alt=""
             class="cover"
             loading="lazy"
+            decoding="async"
         />
     </a>
     <div class="meta">

frontend/src/routes/manga/[id]/+page.svelte

@@ -380,6 +380,7 @@
                     src={fileUrl(manga.cover_image_path)}
                     alt=""
                     loading="eager"
+                    decoding="async"
                 />
             {/if}
             <div class="hero-text">
@@ -401,6 +402,7 @@
                 alt="{manga.title} cover"
                 class="cover"
                 loading="eager"
+                decoding="async"
                 data-testid="manga-cover"
             />
         {/if}
@@ -791,7 +793,10 @@
 
     .cover {
         width: 100%;
-        height: auto;
+        /* Reserve the 2/3 box so the meta column doesn't reflow when the
+           cover decodes (mirrors MangaCard's cover). */
+        aspect-ratio: 2 / 3;
+        object-fit: cover;
         border-radius: var(--radius-md);
         background: var(--surface);
     }