feat(F-189): completed feature

project/apps/pos/src/lib/api-client.ts

@@ -66,6 +66,15 @@ export const posApi = {
       method: 'POST',
       body: JSON.stringify(data),
     }),
+  /** Apply a partial/full return to a POS sale. */
+  createReturn: <T>(orderId: string, data: unknown) =>
+    apiFetch<T>(`/pos/sales/${encodeURIComponent(orderId)}/returns`, {
+      method: 'POST',
+      body: JSON.stringify(data),
+    }),
+  /** List order items for a sale (used by the return UI). */
+  listOrderItems: <T>(orderId: string) =>
+    apiFetch<T>(`/pos/sales/${encodeURIComponent(orderId)}/items`),
   /** List POS sales for the session, optionally filtered by state. */
   listSales: <T>(params?: { state?: 'PENDING' | 'COMPLETED'; sessionId?: string }) => {
     const qs = new URLSearchParams();