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/people.ts

@@ -347,9 +347,12 @@ export async function experts(ctx: Ctx) {
       include: { salesExpertProfile: true },
     });
     if (admin.role !== AdminRole.SALES_EXPERT) {
+      // Owner 2026-10-07: the admin keeps their role. Their expert profile is
+      // still kept, because it is what links their OWN legacy orders (their
+      // trading account) to them — without it their «میزان فروش» lost those
+      // orders. The profile grants nothing: the expert app checks the role.
       ctx.report.count(S, `mobile already an admin with role ${admin.role} — kept, not demoted`);
       ctx.report.note(S, `legacy expert #${String(r.id)} shares a mobile with admin role ${admin.role}; the admin was kept and referrals point to it.`);
-      continue;
     }
     if (!admin.salesExpertProfile) {
       await ctx.db.salesExpertProfile.create({ data: { adminUserId: admin.id, ...profile } });