feat: accounting integration (D27), SMS relay driver (D26), rebuild user apps

- Add Tahesab/Zarrin accounting sync module with admin panel UI
- Add SMS relay driver as default provider, refactor SMS into driver pattern
- Update customer services, orders, products, and catalog queries
- Rebuild user-app and user-app-v2 dist assets
- Add Prisma migration for accounting tables
- Update docker-compose and env examples
- Update parity docs (DECISIONS, ISSUES, PROGRESS)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/api/src/modules/customers/customers.service.ts

@@ -1,6 +1,7 @@
 import { Injectable, NotFoundException } from '@nestjs/common';
 import { Prisma } from '@prisma/client';
 import { PrismaService } from '../../prisma/prisma.service';
+import { AccountingSyncService } from '../accounting-sync/accounting-sync.service';
 
 // passwordHash must never leave the API — every customer read goes through this.
 const PUBLIC_CUSTOMER_SELECT = {
@@ -35,7 +36,10 @@ const PUBLIC_CUSTOMER_SELECT = {
  */
 @Injectable()
 export class CustomersService {
-  constructor(private readonly prisma: PrismaService) {}
+  constructor(
+    private readonly prisma: PrismaService,
+    private readonly accounting: AccountingSyncService,
+  ) {}
 
   async getOrThrow(customerId: string) {
     const customer = await this.prisma.customer.findUnique({
@@ -43,7 +47,21 @@ export class CustomersService {
       select: PUBLIC_CUSTOMER_SELECT,
     });
     if (!customer) throw new NotFoundException(`Customer ${customerId} not found`);
-    return customer;
+
+    // D27 — with the accounting integration on, the customer sees the balance
+    // the accounting software holds. The apps only display these two fields;
+    // the credit-limit check runs server-side on the internal ledger, untouched.
+    const accounting = await this.accounting.customerBalance(customerId);
+    if (accounting) {
+      return {
+        ...customer,
+        goldDebtGrams: accounting.gold,
+        fiatDebtRial: accounting.rial,
+        balanceSource: 'accounting' as const,
+        balanceAt: accounting.at,
+      };
+    }
+    return { ...customer, balanceSource: 'app' as const, balanceAt: null };
   }
 
   getOrders(customerId: string) {