perf: stream slow load functions in admin pages to unblock navigation

- image-gen, text-gen: books list streamed (listBooks is expensive on cold cache)
- ai-jobs: jobs list streamed; add 30s cache to listAIJobs (was uncached listAll)
- changelog: Gitea releases streamed on cold cache; cached path stays synchronous
- admin/+layout.svelte: remove duplicate audio/translation/image-gen nav links

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

@@ -18,23 +18,27 @@ const CACHE_KEY = 'admin:changelog:releases';
 const CACHE_TTL = 5 * 60; // 5 minutes
 
 export const load: PageServerLoad = async ({ fetch }) => {
+	// Return cached data synchronously (no streaming needed — already fast).
 	const cached = await cache.get<Release[]>(CACHE_KEY);
 	if (cached) {
-		return { releases: cached };
+		return { releases: cached, error: undefined as string | undefined };
 	}
 
-	try {
-		const res = await fetch(GITEA_RELEASES_URL, {
-			headers: { Accept: 'application/json' }
-		});
-		if (!res.ok) {
-			return { releases: [], error: `Gitea API returned ${res.status}` };
+	// Cache miss: stream the external Gitea request so navigation isn't blocked.
+	const releasesPromise = (async () => {
+		try {
+			const res = await fetch(GITEA_RELEASES_URL, {
+				headers: { Accept: 'application/json' }
+			});
+			if (!res.ok) return [] as Release[];
+			const releases: Release[] = await res.json();
+			const filtered = releases.filter((r) => !r.draft);
+			await cache.set(CACHE_KEY, filtered, CACHE_TTL);
+			return filtered;
+		} catch {
+			return [] as Release[];
 		}
-		const releases: Release[] = await res.json();
-		const filtered = releases.filter((r) => !r.draft);
-		await cache.set(CACHE_KEY, filtered, CACHE_TTL);
-		return { releases: filtered };
-	} catch (e) {
-		return { releases: [], error: String(e) };
-	}
+	})();
+
+	return { releases: releasesPromise, error: undefined as string | undefined };
 };