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/lib/api/chapters.test.ts

@@ -11,7 +11,8 @@ import {
     listChapters,
     getChapter,
     getChapterPages,
-    createChapter
+    createChapter,
+    chapterLabel
 } from './chapters';
 
 function ok(body: unknown): Response {
@@ -129,6 +130,18 @@ describe('chapters api client', () => {
         }
     });
 
+    describe('chapterLabel', () => {
+        it('returns the site title verbatim when present', () => {
+            expect(chapterLabel({ number: 7, title: 'Ch.7 : Official' })).toBe(
+                'Ch.7 : Official'
+            );
+        });
+
+        it('falls back to "Chapter {number}" when title is null', () => {
+            expect(chapterLabel({ number: 3, title: null })).toBe('Chapter 3');
+        });
+    });
+
     it('getChapterPages unwraps the {pages} envelope into the array', async () => {
         fetchSpy.mockResolvedValueOnce(
             ok({

frontend/src/lib/api/chapters.ts

@@ -14,6 +14,10 @@ export type ChaptersPage = {
     page: Page;
 };
 
+export function chapterLabel(c: Pick<Chapter, 'number' | 'title'>): string {
+    return c.title ?? `Chapter ${c.number}`;
+}
+
 export type ListOptions = {
     limit?: number;
     offset?: number;