perf: cache admin job lists + targeted polling for audio/translation pages

- Add 30s Valkey cache to listScrapingTasks, listAudioJobs, listTranslationJobs
  (use listN(500) instead of unbounded listAll to cap at one request)
- Delete listAudioCache() — derive AudioCacheEntry[] from jobs in server load
- Add listBookSlugs() with 10min cache — replaces full listBooks() in translation load
- Add GET /api/admin/audio-jobs, /api/admin/translation-jobs, /api/admin/scrape-tasks
  (lightweight polling endpoints backed by the Valkey cache)
- Replace invalidateAll() interval polling in audio+translation pages with
  targeted fetch to the new endpoints (avoids re-running full server load)

ui/src/lib/server/pocketbase.ts

@@ -248,6 +248,14 @@ const RATINGS_CACHE_TTL = 5 * 60; // 5 minutes
 const HOME_STATS_CACHE_KEY = 'home:stats';
 const HOME_STATS_CACHE_TTL = 10 * 60; // 10 minutes — counts don't need to be exact
 
+const SCRAPING_TASKS_CACHE_KEY = 'admin:scraping_tasks';
+const AUDIO_JOBS_CACHE_KEY = 'admin:audio_jobs';
+const TRANSLATION_JOBS_CACHE_KEY = 'admin:translation_jobs';
+const ADMIN_JOBS_CACHE_TTL = 30; // 30 seconds — admin views poll frequently
+
+const BOOK_SLUGS_CACHE_KEY = 'books:slugs';
+const BOOK_SLUGS_CACHE_TTL = 10 * 60; // 10 minutes — slugs change rarely
+
 async function getAllRatings(): Promise<BookRating[]> {
 	const cached = await cache.get<BookRating[]>(RATINGS_CACHE_KEY);
 	if (cached) return cached;
@@ -272,6 +280,31 @@ export async function listBooks(): Promise<Book[]> {
 	return books;
 }
 
+export interface BookSlug {
+	slug: string;
+	title: string;
+}
+
+/**
+ * Returns only the slug and title of every book. Cheaper than listBooks() —
+ * used for datalist autocomplete in admin forms. Cached for 10 minutes.
+ */
+export async function listBookSlugs(): Promise<BookSlug[]> {
+	const cached = await cache.get<BookSlug[]>(BOOK_SLUGS_CACHE_KEY);
+	if (cached) return cached;
+	// Re-use full books cache if already warm — avoids a second PocketBase call.
+	const fullCached = await cache.get<Book[]>(BOOKS_CACHE_KEY);
+	if (fullCached) {
+		const slugs = fullCached.map((b) => ({ slug: b.slug, title: b.title }));
+		await cache.set(BOOK_SLUGS_CACHE_KEY, slugs, BOOK_SLUGS_CACHE_TTL);
+		return slugs;
+	}
+	const items = await listAll<BookSlug>('books', '', '+title').catch(() => [] as BookSlug[]);
+	const slugs = items.map((b) => ({ slug: b.slug, title: b.title }));
+	await cache.set(BOOK_SLUGS_CACHE_KEY, slugs, BOOK_SLUGS_CACHE_TTL);
+	return slugs;
+}
+
 /**
  * Fetch only the books whose slugs are in the given set.
  * Uses PocketBase filter `slug IN (...)` — a single request regardless of how
@@ -1052,16 +1085,6 @@ export interface AudioCacheEntry {
 	updated: string;
 }
 
-export async function listAudioCache(): Promise<AudioCacheEntry[]> {
-	const jobs = await listAll<AudioJob>('audio_jobs', 'status="done"', '-finished');
-	return jobs.map((j) => ({
-		id: j.id,
-		cache_key: j.cache_key,
-		filename: `${j.cache_key}.mp3`,
-		updated: j.finished
-	}));
-}
-
 // ─── Scraping tasks ───────────────────────────────────────────────────────────
 
 export interface ScrapingTask {
@@ -1081,7 +1104,11 @@ export interface ScrapingTask {
 }
 
 export async function listScrapingTasks(): Promise<ScrapingTask[]> {
-	return listAll<ScrapingTask>('scraping_tasks', '', '-started');
+	const cached = await cache.get<ScrapingTask[]>(SCRAPING_TASKS_CACHE_KEY);
+	if (cached) return cached;
+	const tasks = await listN<ScrapingTask>('scraping_tasks', 500, '', '-started');
+	await cache.set(SCRAPING_TASKS_CACHE_KEY, tasks, ADMIN_JOBS_CACHE_TTL);
+	return tasks;
 }
 
 export async function getScrapingTask(id: string): Promise<ScrapingTask | null> {
@@ -1103,7 +1130,11 @@ export interface AudioJob {
 }
 
 export async function listAudioJobs(): Promise<AudioJob[]> {
-	return listAll<AudioJob>('audio_jobs', '', '-started');
+	const cached = await cache.get<AudioJob[]>(AUDIO_JOBS_CACHE_KEY);
+	if (cached) return cached;
+	const jobs = await listN<AudioJob>('audio_jobs', 500, '', '-started');
+	await cache.set(AUDIO_JOBS_CACHE_KEY, jobs, ADMIN_JOBS_CACHE_TTL);
+	return jobs;
 }
 
 /**
@@ -1130,7 +1161,11 @@ export interface TranslationJob {
 }
 
 export async function listTranslationJobs(): Promise<TranslationJob[]> {
-	return listAll<TranslationJob>('translation_jobs', '', '-started');
+	const cached = await cache.get<TranslationJob[]>(TRANSLATION_JOBS_CACHE_KEY);
+	if (cached) return cached;
+	const jobs = await listN<TranslationJob>('translation_jobs', 500, '', '-started');
+	await cache.set(TRANSLATION_JOBS_CACHE_KEY, jobs, ADMIN_JOBS_CACHE_TTL);
+	return jobs;
 }
 
 export async function getAudioTime(

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

@@ -1,6 +1,6 @@
 import { redirect } from '@sveltejs/kit';
 import type { PageServerLoad } from './$types';
-import { listAudioCache, listAudioJobs, type AudioCacheEntry, type AudioJob } from '$lib/server/pocketbase';
+import { listAudioJobs, type AudioCacheEntry, type AudioJob } from '$lib/server/pocketbase';
 import { log } from '$lib/server/logger';
 
 export const load: PageServerLoad = async ({ locals }) => {
@@ -8,16 +8,20 @@ export const load: PageServerLoad = async ({ locals }) => {
 		redirect(302, '/');
 	}
 
-	const [entries, jobs] = await Promise.all([
-		listAudioCache().catch((e): AudioCacheEntry[] => {
-			log.warn('admin/audio', 'failed to load audio cache', { err: String(e) });
-			return [];
-		}),
-		listAudioJobs().catch((e): AudioJob[] => {
-			log.warn('admin/audio', 'failed to load audio jobs', { err: String(e) });
-			return [];
-		})
-	]);
+	const jobs = await listAudioJobs().catch((e): AudioJob[] => {
+		log.warn('admin/audio', 'failed to load audio jobs', { err: String(e) });
+		return [];
+	});
+
+	// Derive cache entries from done jobs — no second query needed.
+	const entries: AudioCacheEntry[] = jobs
+		.filter((j) => j.status === 'done')
+		.map((j) => ({
+			id: j.id,
+			cache_key: j.cache_key,
+			filename: `${j.cache_key}.mp3`,
+			updated: j.finished
+		}));
 
 	return { entries, jobs };
 };

ui/src/routes/admin/audio/+page.svelte

@@ -1,6 +1,5 @@
 <script lang="ts">
 	import { untrack } from 'svelte';
-	import { invalidateAll } from '$app/navigation';
 	import type { PageData } from './$types';
 	import type { AudioJob, AudioCacheEntry } from '$lib/server/pocketbase';
 	import * as m from '$lib/paraglide/messages.js';
@@ -21,8 +20,17 @@
 
 	$effect(() => {
 		if (!hasInFlight) return;
-		const id = setInterval(() => {
-			invalidateAll();
+		const id = setInterval(async () => {
+			const res = await fetch('/api/admin/audio-jobs').catch(() => null);
+			if (res?.ok) {
+				const body = await res.json().catch(() => null);
+				if (body?.jobs) {
+					jobs = body.jobs;
+					entries = (body.jobs as AudioJob[])
+						.filter((j) => j.status === 'done')
+						.map((j) => ({ id: j.id, cache_key: j.cache_key, filename: `${j.cache_key}.mp3`, updated: j.finished }));
+				}
+			}
 		}, 3000);
 		return () => clearInterval(id);
 	});

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

@@ -1,6 +1,6 @@
 import { redirect } from '@sveltejs/kit';
 import type { Actions, PageServerLoad } from './$types';
-import { listBooks, listTranslationJobs, type TranslationJob } from '$lib/server/pocketbase';
+import { listBookSlugs, listTranslationJobs, type TranslationJob } from '$lib/server/pocketbase';
 import { backendFetch } from '$lib/server/scraper';
 import { log } from '$lib/server/logger';
 
@@ -10,8 +10,8 @@ export const load: PageServerLoad = async ({ locals }) => {
 	}
 
 	const [books, jobs] = await Promise.all([
-		listBooks().catch((e): Awaited<ReturnType<typeof listBooks>> => {
-			log.warn('admin/translation', 'failed to load books', { err: String(e) });
+		listBookSlugs().catch((e): Awaited<ReturnType<typeof listBookSlugs>> => {
+			log.warn('admin/translation', 'failed to load book slugs', { err: String(e) });
 			return [];
 		}),
 		listTranslationJobs().catch((e): TranslationJob[] => {

ui/src/routes/admin/translation/+page.svelte

@@ -1,6 +1,5 @@
 <script lang="ts">
 	import { untrack } from 'svelte';
-	import { invalidateAll } from '$app/navigation';
 	import { enhance } from '$app/forms';
 	import type { PageData, ActionData } from './$types';
 	import type { TranslationJob } from '$lib/server/pocketbase';
@@ -19,8 +18,12 @@
 
 	$effect(() => {
 		if (!hasInFlight) return;
-		const id = setInterval(() => {
-			invalidateAll();
+		const id = setInterval(async () => {
+			const res = await fetch('/api/admin/translation-jobs').catch(() => null);
+			if (res?.ok) {
+				const body = await res.json().catch(() => null);
+				if (body?.jobs) jobs = body.jobs;
+			}
 		}, 3000);
 		return () => clearInterval(id);
 	});

ui/src/routes/api/admin/audio-jobs/+server.ts

@@ -0,0 +1,16 @@
+import { json, error } from '@sveltejs/kit';
+import type { RequestHandler } from './$types';
+import { listAudioJobs } from '$lib/server/pocketbase';
+
+/**
+ * GET /api/admin/audio-jobs
+ * Returns the current audio jobs list (served from 30 s Valkey cache).
+ * Used by the admin audio page for lightweight polling instead of invalidateAll().
+ */
+export const GET: RequestHandler = async ({ locals }) => {
+	if (!locals.user || locals.user.role !== 'admin') {
+		throw error(403, 'Forbidden');
+	}
+	const jobs = await listAudioJobs().catch(() => []);
+	return json({ jobs });
+};

ui/src/routes/api/admin/scrape-tasks/+server.ts

@@ -0,0 +1,16 @@
+import { json, error } from '@sveltejs/kit';
+import type { RequestHandler } from './$types';
+import { listScrapingTasks } from '$lib/server/pocketbase';
+
+/**
+ * GET /api/admin/scrape-tasks
+ * Returns the current scraping task list (served from 30 s Valkey cache).
+ * Used by the admin scrape page for lightweight polling instead of invalidateAll().
+ */
+export const GET: RequestHandler = async ({ locals }) => {
+	if (!locals.user || locals.user.role !== 'admin') {
+		throw error(403, 'Forbidden');
+	}
+	const tasks = await listScrapingTasks().catch(() => []);
+	return json({ tasks });
+};

ui/src/routes/api/admin/translation-jobs/+server.ts

@@ -0,0 +1,16 @@
+import { json, error } from '@sveltejs/kit';
+import type { RequestHandler } from './$types';
+import { listTranslationJobs } from '$lib/server/pocketbase';
+
+/**
+ * GET /api/admin/translation-jobs
+ * Returns the current translation jobs list (served from 30 s Valkey cache).
+ * Used by the admin translation page for lightweight polling instead of invalidateAll().
+ */
+export const GET: RequestHandler = async ({ locals }) => {
+	if (!locals.user || locals.user.role !== 'admin') {
+		throw error(403, 'Forbidden');
+	}
+	const jobs = await listTranslationJobs().catch(() => []);
+	return json({ jobs });
+};