add Ready to Listen feature: audio book shelf on home + /listen browse page

- getBooksWithAudioCount() in pocketbase.ts aggregates done audio_jobs, deduplicates by chapter per slug, caches 5 min
- GET /api/audio/books endpoint
- home page: readyToListen shelf with headphones badge, chapter count, Listen button, hideable
- /listen page: full grid with search, sort (most narrated / A-Z / recent), empty state

ui/src/routes/+page.server.ts

@@ -6,7 +6,8 @@ import {
 	getHomeStats,
 	getSubscriptionFeed,
 	getTrendingBooks,
-	getRecommendedBooks
+	getRecommendedBooks,
+	getBooksWithAudioCount
 } from '$lib/server/pocketbase';
 import { log } from '$lib/server/logger';
 import type { Book, Progress } from '$lib/server/pocketbase';
@@ -87,8 +88,8 @@ export const load: PageServerLoad = async ({ locals }) => {
 	const inProgressSlugs = new Set(continueReading.map((c) => c.book.slug));
 	const recentlyUpdated = recentBooks.filter((b) => !inProgressSlugs.has(b.slug)).slice(0, 6);
 
-	// Fetch trending, recommendations, and subscription feed in parallel
-	const [trendingBooks, recommendedBooks, subscriptionFeed] = await Promise.all([
+	// Fetch trending, recommendations, subscription feed, and audio books in parallel
+	const [trendingBooks, recommendedBooks, subscriptionFeed, audioBooks] = await Promise.all([
 		getTrendingBooks(8).catch(() => [] as Book[]),
 		topGenres.length > 0
 			? getRecommendedBooks(topGenres, inProgressSlugs, 8).catch(() => [] as Book[])
@@ -98,12 +99,18 @@ export const load: PageServerLoad = async ({ locals }) => {
 					log.error('home', 'failed to load subscription feed', { err: String(e) });
 					return [] as Awaited<ReturnType<typeof getSubscriptionFeed>>;
 				})
-			: Promise.resolve([])
+			: Promise.resolve([]),
+		getBooksWithAudioCount(20).catch(() => [])
 	]);
 
 	// Strip books the user is already reading from trending (redundant)
 	const trendingFiltered = trendingBooks.filter((b) => !inProgressSlugs.has(b.slug));
 
+	// Strip already-reading books from audio shelf; cap at 8
+	const readyToListen = audioBooks
+		.filter((e) => !inProgressSlugs.has(e.book.slug))
+		.slice(0, 8);
+
 	return {
 		continueInProgress,
 		continueCompleted,
@@ -111,6 +118,7 @@ export const load: PageServerLoad = async ({ locals }) => {
 		subscriptionFeed,
 		trendingBooks: trendingFiltered,
 		recommendedBooks,
+		readyToListen,
 		topGenre: topGenres[0] ?? null,
 		stats: {
 			...stats,