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/+layout.svelte

@@ -28,21 +28,6 @@
 			label: () => m.admin_nav_image_gen(),
 			icon: `<path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M4 16l4.586-4.586a2 2 0 012.828 0L16 16m-2-2l1.586-1.586a2 2 0 012.828 0L20 14m-6-6h.01M6 20h12a2 2 0 002-2V6a2 2 0 00-2-2H6a2 2 0 00-2 2v12a2 2 0 002 2z" />`
 		},
-		{
-			href: '/admin/audio',
-			label: () => m.admin_nav_audio(),
-			icon: `<path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 19V6l12-3v13M9 19c0 1.105-1.343 2-3 2s-3-.895-3-2 1.343-2 3-2 3 .895 3 2zm12-3c0 1.105-1.343 2-3 2s-3-.895-3-2 1.343-2 3-2 3 .895 3 2zM9 10l12-3" />`
-		},
-		{
-			href: '/admin/translation',
-			label: () => m.admin_nav_translation(),
-			icon: `<path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M3 5h12M9 3v2m1.048 9.5A18.022 18.022 0 016.412 9m6.088 9h7M11 21l5-10 5 10M12.751 5C11.783 10.77 8.07 15.61 3 18.129" />`
-		},
-		{
-			href: '/admin/image-gen',
-			label: () => m.admin_nav_image_gen(),
-			icon: `<path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M4 16l4.586-4.586a2 2 0 012.828 0L16 16m-2-2l1.586-1.586a2 2 0 012.828 0L20 14m-6-6h.01M6 20h12a2 2 0 002-2V6a2 2 0 00-2-2H6a2 2 0 00-2 2v12a2 2 0 002 2z" />`
-		},
 		{
 			href: '/admin/text-gen',
 			label: () => m.admin_nav_text_gen(),