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/api/scripts/legacy-import/steps/commerce.ts

@@ -50,7 +50,26 @@ export async function orders(ctx: Ctx) {
       continue;
     }
     const orderNumber = `H-${String(r.id)}`;
+    // `orders.reagent_id` is the expert the order was credited to when it was
+    // placed (never moved afterwards) — carried as is, NOT re-derived from the
+    // customer's current referrer (owner ruling 2026-10-08). It names a
+    // Customer row in legacy: an expert maps to their AdminUser; anyone else
+    // (one customer, 17 orders from 2022) is kept as the referrer customer.
+    let salesAgentId: string | null = null;
+    let referrerCustomerId: string | null = null;
+    if (r.reagent_id !== null) {
+      salesAgentId = ctx.map.get('expert', r.reagent_id) ?? null;
+      if (!salesAgentId) referrerCustomerId = ctx.map.get('customer', r.reagent_id) ?? null;
+      if (!salesAgentId && !referrerCustomerId) {
+        ctx.report.count(S, 'placing expert not migrated — left empty');
+        ctx.report.note(S, `legacy order #${String(r.id)}: its reagent #${String(r.reagent_id)} was not migrated`);
+      } else {
+        ctx.report.count(S, salesAgentId ? 'credited to its legacy expert' : 'credited to its legacy referrer customer');
+      }
+    }
     const data = {
+      salesAgentId,
+      referrerCustomerId,
       customerId,
       channel: OrderChannel.WHOLESALE,
       status,
@@ -72,9 +91,7 @@ export async function orders(ctx: Ctx) {
         if (how === 'created') await ctx.db.order.update({ where: { id }, data });
       },
     });
-    ctx.report.count(S, `${res.isNew ? 'created' : 'updated'} — ${status}`);
-    if (r.reagent_id !== null) ctx.report.count(S, 'placing expert (orders.reagent_id) not carried — no target field');
-  }
+    ctx.report.count(S, `${res.isNew ? 'created' : 'updated'} — ${status}`);  }
   await orderItems(ctx);
 }