feat: Implement category and unit selection for inventory items

- Added a new 'category' field to the InventoryItem entity and updated the database schema.
- Replaced free-text input for 'unit' and 'category' with select dropdowns in the AddItemModal.
- Introduced a new API endpoint to fetch metadata for units and categories.
- Updated inventory filtering logic to use the new 'category' field instead of 'consumable'.
- Enhanced validation for item creation and updates to ensure valid unit and category values.
- Updated tests to cover new functionality and ensure proper validation.

assets/admin/hooks/useInventory.ts

@@ -11,6 +11,7 @@ export interface InventoryItem {
   uuid: string;
   name: string;
   consumable: string | null;
+  category: string | null;
   unit: string;
   price: number;          // Rial
   stock: number;
@@ -18,6 +19,12 @@ export interface InventoryItem {
   status: InventoryStatus;
 }
 
+/** Backend-owned option lists (GET /api/v1/inventory-meta) — never hardcode client-side. */
+export interface InventoryMeta {
+  units: string[];
+  categories: string[];
+}
+
 export interface InventoryStats {
   total: number;
   low: number;
@@ -44,6 +51,7 @@ export interface InventoryPackage {
 export interface ItemPayload {
   name: string;
   consumable?: string | null;
+  category?: string | null;
   unit?: string;
   price?: number;
   stock?: number;
@@ -59,6 +67,7 @@ const EMPTY_STATS: InventoryStats = { total: 0, low: 0, inStock: 0, outOfStock:
 const EMPTY_ITEMS: InventoryItem[] = [];
 const EMPTY_PACKAGES: InventoryPackage[] = [];
 const EMPTY_CATS: string[] = [];
+const EMPTY_META: InventoryMeta = { units: [], categories: [] };
 
 // ── Hook ─────────────────────────────────────────────────────────────────────
 
@@ -81,6 +90,13 @@ export function useInventory() {
     queryFn: () => api.get('/api/v1/inventory-categories'),
   });
 
+  // Option lists are effectively static — fetch once, never refetch.
+  const metaQuery = useQuery<ApiResponse<InventoryMeta>>({
+    queryKey: ['inventory-meta'],
+    queryFn: () => api.get('/api/v1/inventory-meta'),
+    staleTime: Infinity,
+  });
+
   const invalidateItems = () => {
     qc.invalidateQueries({ queryKey: ['inventory-items'] });
     qc.invalidateQueries({ queryKey: ['inventory-categories'] });
@@ -125,6 +141,7 @@ export function useInventory() {
     stats: itemsQuery.data?.data?.stats ?? EMPTY_STATS,
     packages: packagesQuery.data?.data ?? EMPTY_PACKAGES,
     categories: categoriesQuery.data?.data ?? EMPTY_CATS,
+    meta: metaQuery.data?.data ?? EMPTY_META,
     itemsLoading: itemsQuery.isLoading,
     packagesLoading: packagesQuery.isLoading,
     createItem, updateItem, deleteItem,