feat: add image optimization and settings page

- Add persistent disk cache for processed images
- Optimize image processing with short-circuit and quality settings
- Add WebP lossy encoding with configurable quality
- Add settings API endpoints (GET/POST /settings, cache management)
- Add database table for app configuration
- Add /settings page in backoffice for image/cache/limits config
- Add cache stats and clear functionality
- Update navigation with settings link

apps/backoffice/app/libraries/page.tsx

@@ -32,8 +32,8 @@ export default async function LibrariesPage() {
   const seriesCounts = await Promise.all(
     libraries.map(async (lib) => {
       try {
-        const series = await fetchSeries(lib.id);
-        return { id: lib.id, count: series.length };
+        const seriesPage = await fetchSeries(lib.id);
+        return { id: lib.id, count: seriesPage.items.length };
       } catch {
         return { id: lib.id, count: 0 };
       }