fix(reader): drop "Chapter N:" prefix from chapter title display (0.51.2)

The chapter list on the manga detail page, the reader's chapter-select
dropdown, the continuous-mode chapter bar, the browser tab title, and
the profile upload-history entries all prepended "Chapter {number}:"
in front of the crawled site title. Source titles already include
"Ch.N" themselves and the manga page renders chapters inside an <ol>,
so the prefix duplicated information the user could already see.

A small chapterLabel(c) helper in $lib/api/chapters returns the site
title as-is, falling back to "Chapter {number}" only when the
crawler captured an empty title (link/option stays non-empty). The
five render sites now call it. The previous-/next-chapter nav
buttons still read "Previous chapter (Ch. N)" / "Next chapter (Ch. N)"
since those are wayfinding labels, not title display.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -10,6 +10,7 @@
         type TagRef
     } from '$lib/api/mangas';
     import { resyncManga } from '$lib/api/admin';
+    import { chapterLabel } from '$lib/api/chapters';
     import { listTags, type Tag } from '$lib/api/tags';
     import { session } from '$lib/session.svelte';
     import Chip from '$lib/components/Chip.svelte';
@@ -45,6 +46,11 @@
         continueChapter?.number ?? readProgress?.chapter_number ?? null
     );
     const continueChapterTitle = $derived(continueChapter?.title ?? null);
+    const continueLabel = $derived(
+        continueChapterNumber != null
+            ? chapterLabel({ number: continueChapterNumber, title: continueChapterTitle })
+            : null
+    );
 
     const authors = $derived<AuthorRef[]>(manga.authors);
     const genres = $derived<GenreRef[]>(manga.genres);
@@ -431,7 +437,7 @@
             >
                 <span class="continue-label">Continue reading</span>
                 <span class="continue-target">
-                    Chapter {continueChapterNumber}{#if continueChapterTitle}: {continueChapterTitle}{/if}
+                    {continueLabel}
                     {#if readProgress && readProgress.page > 1}
                         — page {readProgress.page}
                     {/if}
@@ -445,7 +451,7 @@
                 {#each chapters as c (c.id)}
                     <li>
                         <a href="/manga/{manga.id}/chapter/{c.id}">
-                            Chapter {c.number}{#if c.title}: {c.title}{/if}
+                            {chapterLabel(c)}
                         </a>
                         <span class="pages">({c.page_count} pages)</span>
                     </li>

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

@@ -5,6 +5,7 @@
     import { GAP_PX, type ReaderPageGap } from '$lib/api/preferences';
     import { preferences } from '$lib/preferences.svelte';
     import { updateReadProgress } from '$lib/api/read_progress';
+    import { chapterLabel } from '$lib/api/chapters';
     import { resyncChapter } from '$lib/api/admin';
     import { readerFullscreen } from '$lib/reader-fullscreen.svelte';
     import { session } from '$lib/session.svelte';
@@ -28,9 +29,7 @@
     const gapPx = $derived(GAP_PX[preferences.readerPageGap]);
 
     const pageTitle = $derived(
-        chapter.title
-            ? `Mangalord | ${manga.title} · Ch. ${chapter.number}: ${chapter.title}`
-            : `Mangalord | ${manga.title} · Ch. ${chapter.number}`
+        `Mangalord | ${manga.title} · ${chapterLabel(chapter)}`
     );
 
     // Prev/next chapter computed from the chapter list. listChapters
@@ -474,7 +473,7 @@
             >
                 {#each sortedChapters as c (c.id)}
                     <option value={c.id}>
-                        Ch. {c.number}{c.title ? ` — ${c.title}` : ''}
+                        {chapterLabel(c)}
                     </option>
                 {/each}
             </select>
@@ -685,7 +684,7 @@
             </span>
         </button>
         <span class="chapter-bar-current" aria-hidden="true">
-            Ch. {chapter.number}{#if chapter.title} — {chapter.title}{/if}
+            {chapterLabel(chapter)}
         </span>
         <button
             type="button"

frontend/src/routes/profile/history/+page.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
     import { fileUrl } from '$lib/api/client';
+    import { chapterLabel } from '$lib/api/chapters';
     import { clearReadProgress, type ReadProgressSummary } from '$lib/api/read_progress';
     import BookImage from '@lucide/svelte/icons/book-image';
     import Trash2 from '@lucide/svelte/icons/trash-2';
@@ -186,7 +187,7 @@
                                 <a href="/manga/{u.manga_id}" class="title">{u.manga_title}</a>
                                 <span class="target">
                                     <a href="/manga/{u.manga_id}/chapter/{u.chapter.id}">
-                                        Chapter {u.chapter.number}{#if u.chapter.title}: {u.chapter.title}{/if}
+                                        {chapterLabel(u.chapter)}
                                     </a>
                                     <span class="muted">({u.chapter.page_count} pages)</span>
                                 </span>