Add smoke tests for UOM conversions and enhance frontend UOM management

- Implemented smoke tests for UOM directionality, ensuring conversions are one-directional and correctly validated.
- Added tests for receiving and selling items in different UOMs, verifying correct quantity handling and error responses.
- Created a UOM conversions panel in the frontend to allow users to manage UOM conversions for items.
- Introduced hooks for allowed UOMs to optimize fetching and caching of UOM data for document line forms.
- Developed utility functions for consistent UOM formatting and conversion handling across the application.

Frontend/erp-system/lib/api/items.ts

@@ -3,6 +3,7 @@
 import { apiRequest, apiRequestWithETag, buildQuery } from "@/lib/api-client"
 import { ApiResult, EntityStatus, PagedResponse } from "@/types/common"
 import {
+  AllowedUom,
   CreateItemRequest,
   Item,
   ItemListItem,
@@ -60,10 +61,20 @@ export const itemsApi = {
     })
   },
 
+  /**
+   * Replace the item's conversions. Every row must be `<other> → baseUomId` with a factor
+   * greater than zero; the reverse direction, a self-conversion, or a row from the base UOM
+   * is rejected with 422 (the engine only ever looks up `<other> → base` and never inverts).
+   */
   updateUomConversions(itemId: number, request: UpdateUomConversionsRequest): Promise<UpdateUomConversionsResponse> {
     return apiRequest<UpdateUomConversionsResponse>(`/items/${itemId}/uom-conversions`, {
       method: "PUT",
       body: request,
     })
   },
+
+  /** The UOMs this item can be transacted in — base UOM first, then each conversion source. */
+  allowedUoms(itemId: number): Promise<AllowedUom[]> {
+    return apiRequest<AllowedUom[]>(`/items/${itemId}/uoms`)
+  },
 }