feat(warehouse): add items list and detail pages

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/admin/AdminApp.tsx

@@ -153,6 +153,10 @@ export default function AdminApp() {
                   <Route path="audit-log" element={<AuditLog />} />
                   <Route path="warehouse" element={<Warehouse />} />
                   <Route path="warehouse/items" element={<WarehouseItems />} />
+                  <Route
+                    path="warehouse/items/new"
+                    element={<WarehouseItemDetail />}
+                  />
                   <Route
                     path="warehouse/items/:id"
                     element={<WarehouseItemDetail />}