feat: add per-library download detection auto-schedule

Adds a configurable schedule (manual/hourly/daily/weekly) for the
download detection job in the library settings modal. The indexer
scheduler triggers the job automatically, and the API job poller
processes it — consistent with the reading_status_push pattern.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/backoffice/app/(app)/libraries/page.tsx

@@ -148,6 +148,7 @@ export default async function LibrariesPage() {
                       metadataRefreshMode={lib.metadata_refresh_mode}
                       readingStatusProvider={lib.reading_status_provider}
                       readingStatusPushMode={lib.reading_status_push_mode}
+                      downloadDetectionMode={lib.download_detection_mode ?? "manual"}
                     />
                     <form>
                       <input type="hidden" name="id" value={lib.id} />

apps/backoffice/app/api/libraries/[id]/monitoring/route.ts

@@ -8,8 +8,8 @@ export async function PATCH(
 ) {
   const { id } = await params;
   try {
-    const { monitor_enabled, scan_mode, watcher_enabled, metadata_refresh_mode } = await request.json();
-    const data = await updateLibraryMonitoring(id, monitor_enabled, scan_mode, watcher_enabled, metadata_refresh_mode);
+    const { monitor_enabled, scan_mode, watcher_enabled, metadata_refresh_mode, download_detection_mode } = await request.json();
+    const data = await updateLibraryMonitoring(id, monitor_enabled, scan_mode, watcher_enabled, metadata_refresh_mode, download_detection_mode);
     revalidatePath("/libraries");
     return NextResponse.json(data);
   } catch (error) {

apps/backoffice/app/components/LibraryActions.tsx

@@ -16,6 +16,7 @@ interface LibraryActionsProps {
   metadataRefreshMode: string;
   readingStatusProvider: string | null;
   readingStatusPushMode: string;
+  downloadDetectionMode: string;
   onUpdate?: () => void;
 }
 
@@ -29,6 +30,7 @@ export function LibraryActions({
   metadataRefreshMode,
   readingStatusProvider,
   readingStatusPushMode,
+  downloadDetectionMode,
 }: LibraryActionsProps) {
   const { t } = useTranslation();
   const [isOpen, setIsOpen] = useState(false);
@@ -46,6 +48,7 @@ export function LibraryActions({
       const newMetadataRefreshMode = formData.get("metadata_refresh_mode") as string;
       const newReadingStatusProvider = (formData.get("reading_status_provider") as string) || null;
       const newReadingStatusPushMode = (formData.get("reading_status_push_mode") as string) || "manual";
+      const newDownloadDetectionMode = (formData.get("download_detection_mode") as string) || "manual";
 
       try {
         const [response] = await Promise.all([
@@ -57,6 +60,7 @@ export function LibraryActions({
               scan_mode: scanMode,
               watcher_enabled: watcherEnabled,
               metadata_refresh_mode: newMetadataRefreshMode,
+              download_detection_mode: newDownloadDetectionMode,
             }),
           }),
           fetch(`/api/libraries/${libraryId}/metadata-provider`, {
@@ -313,6 +317,34 @@ export function LibraryActions({
                     </div>
                   </div>
 
+                  <hr className="border-border/40" />
+
+                  {/* Section: Prowlarr */}
+                  <div className="space-y-5">
+                    <h3 className="flex items-center gap-2 text-sm font-semibold text-foreground uppercase tracking-wide">
+                      <svg className="w-4 h-4 text-primary" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                        <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M4 16v1a3 3 0 003 3h10a3 3 0 003-3v-1m-4-4l-4 4m0 0l-4-4m4 4V4" />
+                      </svg>
+                      {t("libraryActions.sectionProwlarr")}
+                    </h3>
+                    <div>
+                      <div className="flex items-center justify-between gap-4">
+                        <label className="text-sm font-medium text-foreground">{t("libraryActions.downloadDetectionSchedule")}</label>
+                        <select
+                          name="download_detection_mode"
+                          defaultValue={downloadDetectionMode}
+                          className="text-sm border border-border rounded-lg px-3 py-1.5 bg-background min-w-[160px] shrink-0"
+                        >
+                          <option value="manual">{t("monitoring.manual")}</option>
+                          <option value="hourly">{t("monitoring.hourly")}</option>
+                          <option value="daily">{t("monitoring.daily")}</option>
+                          <option value="weekly">{t("monitoring.weekly")}</option>
+                        </select>
+                      </div>
+                      <p className="text-xs text-muted-foreground mt-1.5">{t("libraryActions.downloadDetectionScheduleDesc")}</p>
+                    </div>
+                  </div>
+
                   {saveError && (
                     <p className="text-sm text-destructive bg-destructive/10 px-3 py-2 rounded-lg break-all">
                       {saveError}