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/components/inventory/InventoryItemsTable.tsx

@@ -11,7 +11,7 @@ interface Props {
   onDelete: (item: InventoryItem) => void;
 }
 
-const HEAD = ['نام کالا', 'موجودی', 'واحد', 'قیمت', 'وضعیت', 'عملیات'];
+const HEAD = ['نام کالا', 'دسته‌بندی', 'موجودی', 'واحد', 'قیمت', 'وضعیت', 'عملیات'];
 
 /** Consumable-items list: desktop table + mobile card grid (tauri InventoryList). */
 export default function InventoryItemsTable({ items, onEdit, onDelete }: Props) {
@@ -30,6 +30,7 @@ export default function InventoryItemsTable({ items, onEdit, onDelete }: Props)
             {items.map((item) => (
               <tr key={item.uuid}>
                 <td style={{ color: 'var(--text-2)' }}>{item.name}</td>
+                <td style={{ color: 'var(--text-3)' }}>{item.category ?? '—'}</td>
                 <td>{formatNumber(item.stock)}</td>
                 <td>{item.unit}</td>
                 <td>{formatRial(item.price)}</td>
@@ -59,6 +60,7 @@ export default function InventoryItemsTable({ items, onEdit, onDelete }: Props)
               <InventoryStatusBadge status={item.status} />
             </div>
             {[
+              ['دسته‌بندی:', item.category ?? '—'],
               ['موجودی:', formatNumber(item.stock)],
               ['واحد:', item.unit],
               ['قیمت:', formatRial(item.price)],