ADD: Standalone transaction creation page with sidebar menu entry

- Add CreateWarehouseTransaction.vue — full-page form to register IN/OUT transactions
  with item/warehouse dropdowns (searchable), quantity input, reason presets, date picker,
  live stock preview showing current balance for the selected item+warehouse combo,
  and input validation with inline error messages
- Add /warehouse-items/create-transaction route
- Add 'ثبت تراکنش' as first item in 'مدیریت انبار' sidebar group

src/router/index.js

@@ -100,6 +100,11 @@ const router = createRouter({
                     name: 'warehouse-item-stock',
                     component: () => import('@/views/pages/WarehouseItems/WarehouseItemStockView.vue')
                 },
+                {
+                    path: '/warehouse-items/create-transaction',
+                    name: 'create-warehouse-transaction',
+                    component: () => import('@/views/pages/WarehouseItems/CreateWarehouseTransaction.vue')
+                },
                 {
                     path: '/warehouse-items/transactions',
                     name: 'warehouse-item-transactions',