fix: restore complete admin feature dependencies

src/lib/services/watch.ts

@@ -0,0 +1,24 @@
+import { unstable_cache } from 'next/cache'
+import { prisma } from '@/lib/prisma'
+
+/**
+ * Returns the set of user IDs that the given staff member has marked as
+ * "watch". Cached 60s + tag-invalidated by toggleUserWatch.
+ */
+export async function getWatchedUserIds(staffId: number): Promise<Set<number>> {
+  const ids = await getCachedWatchedIds(staffId)
+  return new Set(ids)
+}
+
+const getCachedWatchedIds = unstable_cache(
+  async (staffId: number): Promise<number[]> => {
+    const rows = await prisma.userWatch.findMany({
+      where: { staffId },
+      select: { targetUserId: true },
+    })
+    return rows.map((r) => r.targetUserId)
+  },
+  ['user-watch-list'],
+  { revalidate: 60, tags: ['user-watch'] },
+)
+