feat(orders): credit each order to the expert who placed it, as legacy did

Legacy fixed `orders.reagent_id` once, when the order was placed, and its
«میزان فروش» summed `customer_id = X OR reagent_id = X`. The app credited
orders to the customer's CURRENT referrer and left out an expert's own
orders, so 9 of 49 imported experts showed a different figure.

- Order.salesAgentId (+ referrerCustomerId for 17 legacy orders whose
  referrer was not an expert); additive migration, recent app orders
  backfilled from the customer's referrer
- createOrder records the expert at placement time
- one shared filter (agent-orders.ts) for the experts list, expert
  detail, dashboard and the expert app; child orders follow salesAgentId
- customer page gets its «میزان فروش» back
- import carries orders.reagent_id as is; ex-experts kept as admins keep
  their profile so their own orders stay linked
- reconcile-sales: 1,557 of 1,558 match legacy's own formula; balances
  unchanged

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/admin-panel/src/views/customer/CustomerDetail.vue

@@ -33,6 +33,8 @@
         <a-descriptions-item label="بدهی ریالی">
           {{ customer?.rial_remain ?? '-' }}
         </a-descriptions-item>
+        <!-- legacy ViewOmdeCustomer.vue:28-30 -->
+        <a-descriptions-item label="میزان فروش">{{ dashboard?.grams_sell ?? '-' }}</a-descriptions-item>
       </a-descriptions>
 
       <div v-if="dashboard" class="stats mt-4">