feat: group thousands in inventory item price input

Show the قیمت (تومان) field with thousand separators as the user types
(e.g. 1200000 → 1,200,000). Stored value stays digit-only, so the
Toman→Rial conversion on submit is unaffected.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

assets/admin/components/inventory/AddItemModal.tsx

@@ -23,6 +23,8 @@ interface FormState {
 const BLANK: FormState = { name: '', consumable: '', unit: '', price: '', stock: '', alertThreshold: '' };
 
 const digits = (v: string) => toEnglishDigits(v).replace(/\D/g, '');
+// group thousands: "1200000" → "1,200,000"
+const group = (v: string) => v.replace(/\B(?=(\d{3})+(?!\d))/g, ',');
 
 /** «افزودن/ویرایش کالای جدید» — mirrors tauri ModalAddInventory field-for-field. */
 export default function AddItemModal({ open, editing, saving, onClose, onSave }: Props) {
@@ -79,7 +81,7 @@ export default function AddItemModal({ open, editing, saving, onClose, onSave }:
             <label className="field-label">{f.label}</label>
             <div className="field">
               <input
-                value={form[f.key]}
+                value={f.key === 'price' ? group(form.price) : form[f.key]}
                 onChange={f.numeric ? setNum(f.key) : set(f.key)}
                 placeholder={f.placeholder}
                 inputMode={f.numeric ? 'numeric' : undefined}