fix(ui): fix chapter page SSR crash by lazy-loading marked

Static import of 'marked' was included in the SSR bundle causing
ERR_MODULE_NOT_FOUND on first server render. The import is only
ever used inside onMount (client-only fallback path), so replace
with a dynamic import() at the call site.

ui/src/routes/books/[slug]/chapters/[n]/+page.svelte

@@ -2,7 +2,6 @@
 	import { onMount } from 'svelte';
 	import AudioPlayer from '$lib/components/AudioPlayer.svelte';
 	import type { PageData } from './$types';
-	import { marked } from 'marked';
 
 	let { data }: { data: PageData } = $props();
 
@@ -42,6 +41,7 @@
 				if (!res.ok) throw new Error(`status ${res.status}`);
 				const d = (await res.json()) as { text?: string };
 				if (d.text) {
+					const { marked } = await import('marked');
 					html = await marked(d.text, { async: true });
 				} else {
 					fetchError = 'Chapter content not available.';