feat(web/m7-recurring-scans): scan-schedule API client + query

Adds ScanSchedule type, getScanSchedule / updateScanSchedule
against the new admin endpoints, createScanScheduleQuery (60s
staleTime; refetches on focus + after PATCH invalidation — no
polling).

New qk.scanSchedule() key follows the existing tuple pattern.
ScanScheduleUpdate uses optional fields so mode=off updates can
omit per-mode fields entirely (server normalizes anyway).

Vitest covers the GET path, PATCH with body, and the mode=off
minimal-body case.

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

web/src/lib/api/admin.ts

@@ -329,3 +329,40 @@ export function createCoverProvidersQuery() {
     staleTime: 60_000
   });
 }
+
+// Scan schedule -----------------------------------------------------------
+
+export type ScanScheduleMode = 'off' | 'interval' | 'daily' | 'weekly';
+
+export type ScanSchedule = {
+  mode: ScanScheduleMode;
+  interval_hours: number | null;
+  time_of_day: string | null;       // 'HH:MM'
+  weekly_day: number | null;        // 1..7 (Mon..Sun, ISO 8601)
+  next_scheduled_at: string | null; // RFC3339 ISO timestamp; null when mode='off'
+};
+
+export type ScanScheduleUpdate = {
+  mode: ScanScheduleMode;
+  interval_hours?: number | null;
+  time_of_day?: string | null;
+  weekly_day?: number | null;
+};
+
+export async function getScanSchedule(): Promise<ScanSchedule> {
+  return api.get<ScanSchedule>('/api/admin/scan/schedule');
+}
+
+export async function updateScanSchedule(patch: ScanScheduleUpdate): Promise<ScanSchedule> {
+  return api.patch<ScanSchedule>('/api/admin/scan/schedule', patch);
+}
+
+// Settings rarely change in operator time. 60s staleTime; refetches
+// on window focus + after any PATCH invalidation — no polling.
+export function createScanScheduleQuery() {
+  return createQuery({
+    queryKey: qk.scanSchedule(),
+    queryFn: getScanSchedule,
+    staleTime: 60_000
+  });
+}