- Add listGlobalItemsForAdmin: paginated with batched tag/ownerCount queries
- Add updateGlobalItemById: partial update in transaction, syncs tags
- Add deleteGlobalItem: nullifies FK refs, removes tag associations before delete
- Create src/server/routes/admin-items.ts with GET/GET:id/PUT/DELETE endpoints
- Mount adminItemRoutes at /items in admin.ts (protected by requireAuth+requireAdmin)
- Extend global-item.service.test.ts with 13 new tests (all passing)
Closes ADMN-02, ADMN-03, ADMN-04 (server side)